# How to fix a slow computer: diagnose it by symptom, then fix the cause

> Fix a slow Windows 11 PC by symptom: slow start-up, 100% disk, a busy processor, full memory, a slow browser or Wi-Fi, or slowness after an update.

- URL: https://computese.com/how-to-fix-a-slow-computer-practical-tips-2024/
- Author: Duong Quan Nguyen, CEO, Computese
- Published: 2024-09-27
- Updated: 2026-09-25
- Topics: IT support

## In short
- Fix a slow computer by symptom: note when it is slow, then confirm the cause in Task Manager (Ctrl + Shift + Esc) before changing anything, because each bottleneck has a different fix.
- Slow start-up points at High-impact startup apps, a disk stuck at 100% at one busy process or a failing drive, a slow browser at tabs or extensions, and slow Wi-Fi at the network rather than the PC.
- If the PC slowed down suddenly, Reliability Monitor (perfmon /rel) shows what was installed on the day it started; roll back that driver or uninstall that update.
- Heat and battery settings slow a healthy PC on purpose: a hot processor throttles its clock speed, and power modes limit background work to save energy.
- If nothing helps, follow Microsoft's recovery order: troubleshooter, reinstall Windows in place, uninstall updates, point-in-time restore, and Reset this PC last, after a backup.

To fix a slow computer, name the symptom first and confirm its cause before changing anything. Task Manager shows whether the processor, memory, disk or network is the limit; Reliability Monitor shows what changed on the day it slowed down. Each cause then has its own fix, from disabling one startup app to rolling back one driver.

This guide is organized by symptom: slow start-up, a disk stuck at 100%, one process hogging the processor, memory running out, a slow browser, slow Wi-Fi, slowness after an update, heat and battery, and malware. For each one you get how to confirm it and the fix, using tools built into Windows 11, with menu names as of September 2026 ([version 25H2](https://learn.microsoft.com/en-us/windows/release-health/windows11-release-information), the current release for existing PCs). If nothing is broken and you want to tune the settings instead, our guide to [optimizing PC performance in Windows 11](https://computese.com/how-to-optimize-pc-performance/) covers power mode, visual effects, Storage Sense and virtual memory step by step. If you just want the common quick fixes in one pass, start with the [15-minute speed-up checklist](https://computese.com/how-to-speed-up-a-slow-computer/); if you want to understand what each cause does to memory, disk and processor, read [why is my computer so slow](https://computese.com/why-is-your-computer-slow-and-how-to-fix/). A short section at the end covers the Mac.

## Start here: which kind of slow is it?

Before anything else, close the apps and browser tabs you are not using, and restart if that does not help. [Microsoft's own list of fixes](https://support.microsoft.com/en-us/windows/experience/performance-optimization/tips-to-improve-pc-performance-in-windows) ends with exactly that, because many open apps and tabs slow a PC by themselves. If the slowness comes back, note when it happens and match it here:

| When it is slow                                   | Confirm it with                         | Section below    |
| ------------------------------------------------- | --------------------------------------- | ---------------- |
| At start-up, or for minutes after you sign in     | Task Manager > **Startup apps**         | Slow start-up    |
| Everything stalls; the Disk column sits near 100% | Task Manager > **Processes**, by Disk   | Disk at 100%     |
| Fans loud; one process tops the CPU column        | Task Manager > **Processes**, by CPU    | One process      |
| Worse with every app or tab you open              | Task Manager > **Performance > Memory** | Memory full      |
| Only in the browser                               | Other apps stay quick                   | Slow browser     |
| Only websites, downloads and calls                | Another device on the same Wi-Fi        | Network          |
| Since an update, a new driver or a new app        | Reliability Monitor, Update history     | After an update  |
| When the PC is hot, or only on battery            | Fan noise, heat, power mode             | Heat and battery |
| An unfamiliar process keeps busy                  | A Windows Security scan                 | Malware          |

Task Manager is the first tool for almost every row. Press **Ctrl + Shift + Esc**, or right-click **Start** and select **Task Manager**. On the **Processes** page, select a column header such as **CPU**, **Memory** or **Disk** to sort by it, highest first: the process at the top is the one using that resource now. The **Performance** page draws each resource over time.

Judge what you see over minutes, not seconds. [Microsoft's guidance on high CPU usage](https://learn.microsoft.com/en-us/troubleshoot/windows-server/performance/troubleshoot-high-cpu-usage-guidance) calls short spikes normal and treats usage that stays at 80 percent or higher for extended periods as the problem worth chasing. For an average over time instead of a snapshot, open **Resource Monitor** (type `resmon` in Start, or run [`perfmon /res`](https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/perfmon)) and, on its **CPU** tab, sort by **Average CPU**.

## Slow to start up, or slow right after you sign in

Slow start-up has two shapes: the PC takes a long time to reach the desktop, or it gets there quickly and then stays sluggish for the first few minutes. Either way, check the apps that start with Windows first. [Microsoft notes](https://support.microsoft.com/en-us/windows/experience/startup-boot/configure-startup-applications-in-windows) that they affect both how fast the device starts and how the system performs afterwards.

1. Open Task Manager and select **Startup apps**. The **Startup impact** column rates each app from what it cost at start-up: **High** means more than 1 second of processor time or more than 3 MB of disk activity.
2. Select each High-impact app you do not need the moment you sign in, and select **Disable**. It stops starting automatically; you can still open it yourself.
3. Restart and compare.

The same list, with a switch per app, is in **Settings > Apps > Startup**. An app missing from both may start from a startup folder instead: press **Windows + R**, type `shell:startup` and delete its shortcut there. Our [optimization guide](https://computese.com/how-to-optimize-pc-performance/) has the full impact table and what is usually safe to switch off.

### Find a cause that is not on the list: clean boot

Windows services do not appear in the startup apps list. If disabling startup apps does not help, a [clean boot](https://support.microsoft.com/en-us/windows/experience/startup-boot/how-to-perform-a-clean-boot-in-windows) starts Windows with only essential drivers and startup programs, which shows whether third-party software is the cause at all:

1. Sign in as an administrator, type `msconfig` in Start and open **System Configuration**.
2. On the **Services** tab, select **Hide all Microsoft services**, then **Disable all**, then **Apply**.
3. On the **Startup** tab, select **Open Task Manager** and disable every enabled startup app, noting which ones you changed.
4. Restart. If the PC is now quick, one of the disabled items is the cause: re-enable the upper half of the services, restart, and keep halving until you find it, then do the same with the startup apps.
5. When you are done, choose **Normal startup** on the **General** tab and re-enable what you disabled.

> [!WARNING]
> Stay on the **Services** and **Startup** tabs. Microsoft warns that System Configuration might make the computer unusable, and says to change its advanced boot options only with guidance from a Microsoft support engineer.

If start-up is slow and the PC also freezes now and then, check the drive's health (next section) before anything else.

## Disk at 100%: find what is using it

When Task Manager's **Disk** column sits at or near 100%, the drive is overwhelmed: reads and writes queue behind each other, and every program that needs the disk waits its turn, which is why the whole PC seems to freeze. That is a different problem from a full drive, which shows in **Settings > System > Storage** and which Microsoft lists separately: [low disk space can reduce performance too](https://support.microsoft.com/en-us/windows/experience/performance-optimization/tips-to-improve-pc-performance-in-windows).

![Four program windows send small request blocks to one storage drive, where the blocks wait in a single long queue. The window sending the most requests, marked with a magnifying glass, is orange.](https://computese.com/images/blog/how-to-fix-a-slow-computer-practical-tips-2024/disk-queue.d296ecf16d-1536.webp)

*At 100%, requests wait in line for the drive; the fix is finding the one process that sends most of them.*

To confirm it and find the source:

1. In Task Manager > **Processes**, sort by **Disk** and note the top process. Short bursts are normal; a process that stays on top for many minutes is the one to deal with.
2. Measure how long the drive takes to answer. Microsoft's [performance troubleshooting guide](https://learn.microsoft.com/en-us/troubleshoot/windows-server/performance/troubleshoot-performance-problems-in-windows) treats an average read or write time under 15 ms as healthy, above 25 ms as a warning and above 50 ms as critical, when it lasts a minute or more. In PowerShell, [`Get-Counter`](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.diagnostics/get-counter) samples those counters every 5 seconds for a minute. The values are in seconds, so 0.015 is 15 ms:

```powershell
Get-Counter -Counter '\PhysicalDisk(*)\Avg. Disk sec/Read','\PhysicalDisk(*)\Avg. Disk sec/Write' -SampleInterval 5 -MaxSamples 12
```

What the top process tells you:

- **Windows Search indexing.** The first full index [can take up to a couple of hours](https://support.microsoft.com/en-us/windows/experience/performance-optimization/search-indexing-in-windows); after that, it re-indexes only what changed. If indexing never settles, open **Settings > Privacy & security > Search**: **Enhanced** mode indexes the entire PC and may use more resources, while **Classic** covers Documents, Pictures, Music and the desktop.
- **Your antivirus.** A [full scan](https://support.microsoft.com/en-us/windows/security/threat-malware-protection/virus-and-threat-protection-in-the-windows-security-app) checks every file and program on the device, so the disk stays busy until it finishes. Let it complete.
- **Memory running short.** If Task Manager also shows memory close to its limit (see the memory section), Windows is writing memory pages to the [page file](https://learn.microsoft.com/en-us/troubleshoot/windows-client/performance/introduction-to-the-page-file) on disk. Fix the memory problem and the disk load drops with it.
- **Nothing obvious.** If no process explains the load, or the drive is slow even when little is running, check its health.

### Check the drive's health

Windows 11 reads health data from NVMe solid-state drives. Go to **Settings > System > Storage > Advanced storage settings > Disks & volumes**, select the drive and choose **Properties**. **Drive health** shows the [estimated remaining life, the available spare capacity and the temperature](https://support.microsoft.com/en-us/windows/experience/storage-filemanagement/what-to-do-about-a-critical-warning-for-a-storage-device), and Windows raises a critical warning when spare capacity falls below the manufacturer's threshold, when media errors have degraded reliability, or when the drive has switched to read-only. Microsoft lists device slowness, freezing and longer start-up times among the symptoms. Windows monitors only NVMe drives this way, not SATA SSDs or hard disk drives.

For those, ask PowerShell, opened as administrator. [`Get-PhysicalDisk`](https://learn.microsoft.com/en-us/powershell/module/storage/get-physicaldisk) reports each drive's health status, and [`Get-StorageReliabilityCounter`](https://learn.microsoft.com/en-us/powershell/module/storage/get-storagereliabilitycounter) reads the counters a drive keeps about its temperature, errors, wear and hours in use:

```powershell
Get-PhysicalDisk | Format-Table FriendlyName, HealthStatus, OperationalStatus
Get-PhysicalDisk | Get-StorageReliabilityCounter | Format-List Temperature, Wear, ReadErrorsUncorrected, WriteErrorsUncorrected, PowerOnHours
```

A blank field means the drive does not report that counter; even Microsoft's own example output leaves **Wear** empty. A health status other than Healthy, or uncorrected errors that keep growing, are reasons to back up now and plan a replacement.

> [!IMPORTANT]
> A drive health warning is a backup problem before it is a speed problem. Microsoft's advice for a critical storage warning starts with backing up your data, so copy what matters off the drive before you try any other fix.

## One process keeps the processor busy

Sort Task Manager's **Processes** page by **CPU**. If one entry stays at the top while you are not using it, that is the process to deal with, and what you do depends on what it is:

- **An app you recognize**, such as a browser, a chat or sync client, or a game launcher: close it, update it, and if it keeps doing this, take it to the vendor, as [Microsoft advises for third-party processes](https://learn.microsoft.com/en-us/troubleshoot/windows-server/performance/troubleshoot-high-cpu-usage-guidance).
- **Service Host (svchost.exe).** One Service Host process can hold several Windows services. Expand the group in Task Manager to see which services are inside; Microsoft's procedure for a busy svchost starts by finding which of its services drives the usage.
- **A name you do not recognize**, especially one that comes back after you end it: scan for malware first (see the malware section).

For a program that is legitimately busy in the background, Task Manager's **Efficiency mode** helps. [Microsoft describes it](https://support.microsoft.com/en-us/edge/learn-about-performance-features-in-microsoft-edge) as limiting the resources a process uses by lowering its priority, so the apps in front of you stay responsive; our [optimization guide](https://computese.com/how-to-optimize-pc-performance/) shows where to switch it on.

## Memory is full: commit charge and too many tabs

Memory trouble has its own pattern: the PC is fine with a few apps open and gets slower with every app or tab you add. To confirm it, open Task Manager > **Performance > Memory** and read **Committed**. It shows the commit charge, the memory Windows has promised to programs, against the commit limit, which is physical RAM plus the page file. [Microsoft's introduction to the page file](https://learn.microsoft.com/en-us/troubleshoot/windows-client/performance/introduction-to-the-page-file) explains the stakes: when the commit charge reaches the limit, the system and programs may not get the memory they ask for, which can cause freezing and crashing.

- **Committed stays well below the limit**, even at your busiest: memory is not the bottleneck; look at the other rows of the table.
- **Committed runs close to the limit**: sort the **Processes** page by **Memory**, close what you do not need, and restart. If your normal workload reaches the limit, the lasting fixes are fewer programs at once or more RAM, not a bigger page file (the optimization guide explains why).

Browsers are the usual heavy user. [Google's own advice](https://support.google.com/chrome/answer/1385029) is that Chrome works harder with every open tab, so close the tabs you are not using. Both major browsers can also put idle tabs to sleep:

- **Chrome:** **Settings > Performance > Memory Saver** deactivates tabs you are not using and reloads them when you return. [Choose a level](https://support.google.com/chrome/answer/12929150): **Moderate**, **Balanced** (recommended) or **Maximum**, which makes tabs inactive soonest.
- **Microsoft Edge:** [sleeping tabs](https://support.microsoft.com/en-us/edge/learn-about-performance-features-in-microsoft-edge) puts background tabs to sleep after two hours of inactivity by default; shorten the interval at `edge://settings/system`. Edge's performance detector also flags background tabs that use a lot of memory or processor time and offers to fix them.

## Only the browser is slow

If other apps stay quick and only the browser crawls, first rule out the network: open the same page in a second browser. [Microsoft's Edge troubleshooting guide](https://support.microsoft.com/en-us/edge/what-to-do-if-microsoft-edge-isn-t-working) uses the same test; if the page fails in the other browser too, the problem is the network or the website. If only one browser is slow, work through it in this order:

1. **Find the heavy tab or extension.** In Chrome, open **More > More tools > Task Manager**, sort by **Memory**, and [end the tasks you no longer need](https://support.google.com/chrome/answer/1385029); Google suggests looking for items labelled "Background page".
2. **Test without extensions.** [Google's procedure](https://support.google.com/chrome/answer/6138475): open the page in an Incognito window, and if it works there, turn off all extensions, then turn them back on one at a time until the problem returns, and remove that one. For Edge, [Microsoft suggests](https://support.microsoft.com/en-us/edge/what-to-do-if-microsoft-edge-isn-t-working) uninstalling the extensions you do not need.
3. **Update the browser.** Chrome works best on the latest version, and in Edge, **Settings > About Microsoft Edge** applies any pending update.
4. **Toggle graphics acceleration.** Both browsers have a setting called **Use graphics acceleration when available**, which is on unless a policy turns it off ([Edge](https://learn.microsoft.com/en-us/deployedge/microsoft-edge-policies/hardwareaccelerationmodeenabled), [Chrome](https://chromeenterprise.google/policies/#HardwareAccelerationModeEnabled)). Search for "acceleration" in the browser's settings. If scrolling and video stutter, turn it off, restart the browser and compare; turn it back on if it made no difference.
5. **Reset or repair.** [Chrome's reset](https://support.google.com/chrome/answer/3296214) (**Settings > Reset settings > Restore settings to their original defaults**) returns the search engine, start-up and pinned tabs, site settings, cookies, and extensions and themes to their defaults, while keeping bookmarks and saved passwords. Edge can be repaired from **Settings > Apps > Installed apps > Microsoft Edge > Modify > Repair**, which Microsoft says should not affect your browser data and settings.

## Only the network or Wi-Fi is slow

A PC that opens local files instantly but loads websites, downloads and video calls slowly has a network problem, not a computer problem. Confirm it the way [Microsoft's Wi-Fi guide](https://support.microsoft.com/en-us/windows/experience/connectivity-networking/fix-wi-fi-connection-issues-in-windows) suggests: connect another device to the same Wi-Fi. If that one is slow too, the router or the internet connection is the issue, and the router may need maintenance or replacement.

If only this PC is slow:

1. **Look for a process using the connection.** In Task Manager, end processes that are using a lot of network bandwidth and that you do not need right now, such as a large download.
2. **Check the signal.** Move closer to the router, with fewer obstructions in between.
3. **Run the troubleshooter.** On Windows 11, the **Network and Internet** troubleshooter in the **Get Help** app runs diagnostics and tries to fix most problems by itself.
4. **Stop the adapter saving power.** If the connection keeps dropping, open **Control Panel > Hardware and Sound > Power Options**, select **Change plan settings > Change advanced power settings**, expand **Wireless Adapter Settings** and set **Power Saving Mode** to **Maximum Performance**. Changing the router's wireless channel can also reduce interference.
5. **Restart the modem and router.** This creates a new connection to your internet provider, and briefly disconnects everyone on the network.
6. **Reset the network settings last.** **Network reset** removes every network adapter and its settings, then reinstalls them with defaults after a restart, which is why Microsoft lists it as the last step to try.

## Slow since an update or a new driver: find what changed

When a PC that was fine last week is slow now, look for what changed. Two built-in tools show what changed and when.

**Reliability Monitor** is the quicker one. Type "reliability" in Start and select **View reliability history**, or run [`perfmon /rel`](https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/perfmon); [Dell's guide](https://www.dell.com/support/kbdoc/en-us/000178177/how-to-use-windows-reliability-monitor-to-identify-software-issues) walks through both routes. It draws one column per day. Along the top runs the [System Stability Index](https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-r2-and-2008/cc749032%28v=ws.10%29), from 1 (least stable) to 10 (most stable), weighted towards recent failures. Below it, icons mark [software installs and removals](https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-r2-and-2008/cc749583%28v=ws.10%29), including Windows updates and drivers, and failures of applications, Windows and hardware, kept for up to a year. Find the day the line dropped, select that column, and read what was installed that day and what failed after it.

![A calendar-like chart of day columns with a line graph that drops sharply on one day. In that column an orange package with a downward arrow marks an install; failure marks appear from that day on.](https://computese.com/images/blog/how-to-fix-a-slow-computer-practical-tips-2024/reliability.b6387ed2d2-1536.webp)

*Installs and failures share one timeline, so the change that started the trouble lines up with the day it began.*

**Event Viewer** holds the detail. Open it from Start, select the **System** or **Application** log (under **Windows Logs**), and open an event to read its description, as [Microsoft's startup troubleshooting guide](https://learn.microsoft.com/en-us/troubleshoot/windows-client/performance/windows-boot-issues-troubleshooting) describes. Look at the errors and warnings from the time the slowness began; an error that repeats every few minutes is worth searching by its source and event ID.

**Update history** is the simplest list of all: **Settings > Windows Update > Update history** shows which updates were installed, and when ([Windows Update FAQ](https://support.microsoft.com/en-us/windows/deployment/updates-lifecycle/windows-update-faq)).

Then undo the change that lines up with the slowdown:

1. **A driver updated that day.** Right-click **Start**, open **Device Manager**, expand the category, right-click the device and select **Properties > Driver > Roll Back Driver**, choose a reason and confirm. You need administrator rights, and [Microsoft notes](https://support.microsoft.com/en-us/windows/update-drivers-through-device-manager-in-windows-ec62f46c-ff14-c91d-eead-d7126dc1f7b6) that when a problem starts after a Windows update, reinstalling the previous driver often resolves it.
2. **A Windows update.** Go to **Settings > Windows Update > Update history > Uninstall updates**, select the update and choose **Uninstall**. Not every update can be removed, and Microsoft does not recommend removing updates unless it is necessary, so treat this as a test: if the PC is quick again, install the next fixed update rather than staying unpatched.
3. **A new version of Windows.** After a feature upgrade, [you can go back to the previous version for 10 days](https://support.microsoft.com/en-us/windows/experience/backup-recovery/recovery-options-in-windows).
4. **Several changes at once**, or you cannot tell which: System Restore rolls back system files and settings but not personal files. On Windows 11 version 24H2 and later, point-in-time restore rolls the whole PC back to a recent automatic restore point, including apps, settings and personal files, so anything changed after that point is lost.

## Slow when hot or on battery: throttling and power mode

Two things slow a healthy PC on purpose: heat, to protect the hardware, and power settings, to save energy.

**Heat.** [Intel describes throttling](https://www.intel.com/content/www/us/en/support/articles/000088048/processors.html) as a mechanism that reduces the processor's clock speed when its temperature goes above its maximum (TjMax), both to protect the processor and to show that the system is overheating. The pattern to look for: a heavy task starts at full speed, then slows as the fans get loud and the case gets hot; in games it shows as stutter. Intel's checklist is the cooling: a fan that works, air that can get in and out, and a cooler fitted correctly with the right amount of thermal paste. On laptops the manufacturer sets the power limits, so its support tools and service are the place to take a laptop that throttles when clean.

![A laptop drawn open from above shows its processor, a heat pipe, cooling fins and a fan. Dust covers the fins, airflow arrows turn back inside, and a gauge on the orange processor points low.](https://computese.com/images/blog/how-to-fix-a-slow-computer-practical-tips-2024/throttle.6370063394-1536.webp)

*Heat that cannot leave the case makes the processor slow itself down; clear the airflow and the speed comes back.*

Blocked vents and dusty fans are what a careful cleaning fixes. Our guide to [cleaning computer hardware safely](https://computese.com/how-to-safely-clean-your-computers-hardware/) covers vents, fans and when to replace thermal paste.

**Battery.** Windows 11 keeps a separate [power mode](https://support.microsoft.com/en-us/windows/change-the-power-mode-for-your-windows-pc-c2aff038-22c9-f46d-5ca0-78696fdf2de8) for **Plugged in** and **On battery** in **Settings > System > Power & battery**. [Best power efficiency](https://support.microsoft.com/en-us/windows/experience/power-battery/power-settings-in-windows-11) saves power by limiting background activity, and **Energy saver** turns on when the battery is low, dims the screen and limits background processes. A laptop that is quick on the charger and slow on battery is usually doing exactly what those settings ask. If you need the speed away from the charger, set **On battery** to **Balanced** or **Best performance**, and accept that [the battery drains faster and the laptop may run warmer](https://support.microsoft.com/en-us/windows/experience/performance-optimization/tips-to-improve-pc-performance-in-windows). If **Power mode** cannot be changed, a custom power plan is selected: choose **Balanced** in **Control Panel > System and Security > Power Options**. Our guide to [extending laptop battery life](https://computese.com/how-to-extend-your-laptops-battery-life/) covers the other side of that trade.

## Slow because of malware or unwanted software

[Malware can consume processor and disk resources](https://support.microsoft.com/en-us/windows/experience/performance-optimization/tips-to-improve-pc-performance-in-windows), so a scan belongs on the list whenever the cause is not obvious, and first when an unfamiliar process is busy. Open **Settings > Privacy & security > Windows Security > Virus & threat protection** and run a **Quick scan**.

If it finds something, or the PC still seems wrong, run the [Microsoft Defender Antivirus (offline scan)](https://support.microsoft.com/en-us/windows/security/threat-malware-protection/virus-and-threat-protection-in-the-windows-security-app) from **Scan options**. It restarts the PC and scans without loading Windows, where persistent malware has a harder time hiding or defending itself; the results appear afterwards under **Protection history**. For choosing protection beyond what Windows includes, see our guide to [choosing antivirus software for your PC](https://computese.com/choose-the-right-antivirus-software-for-your-pc/).

## On a Mac: Activity Monitor

The same method works on a Mac with Activity Monitor. It [lists processes](https://support.apple.com/guide/activity-monitor/view-information-about-processes-actmntr1001/mac) with how much memory and CPU time each uses; click a column heading to sort. For memory, open the **Memory** pane and read the [Memory Pressure graph](https://support.apple.com/guide/activity-monitor/check-if-your-mac-needs-more-ram-actmntr34865/mac): green means the Mac is using its RAM efficiently, yellow that it might eventually need more, and red that it needs more RAM. Apple also points out that free memory by itself does not make a Mac faster, because macOS performs best when it uses and manages all of its memory. The **Energy**, **Disk** and **Network** panes cover the other rows of the symptom table.

## When none of this fixes it

If the PC does not start at all, or crashes with a stop code, that is [a fault to troubleshoot](https://computese.com/how-to-troubleshoot-common-pc-problems/) rather than a slowdown. If it starts but stays slow after the steps above, [Microsoft's recovery options](https://support.microsoft.com/en-us/windows/experience/backup-recovery/recovery-options-in-windows) for a PC that is slow, crashing or freezing run from least to most disruptive:

1. Run a troubleshooter: **Settings > System > Troubleshoot > Other troubleshooters**.
2. Reinstall Windows in place, which reinstalls the current version without affecting your files, apps or settings (Windows 11 version 22H2 and later).
3. Uninstall a recent update, or go back to the previous version within 10 days of an upgrade.
4. Point-in-time restore (Windows 11 version 24H2 and later).
5. **Reset this PC**, which reinstalls Windows from scratch and either keeps your personal files or removes everything.

Back up before you start: Microsoft warns that some recovery options can result in data loss.

Be realistic about age, too. [Microsoft says](https://support.microsoft.com/en-us/windows/experience/performance-optimization/tips-to-improve-pc-performance-in-windows) that older PCs with outdated hardware may not see significant improvements from these steps, and that upgrading the device may then be the best long-term solution; our guide to [upgrading a PC for better performance](https://computese.com/guide-to-optimizing-your-pc-for-peak-performance/) covers which part to change first, and when to replace the PC instead.

When slow PCs are a recurring ticket across a team, our [IT support service](https://computese.com/services/it-support/) traces recurring issues to their cause and fixes them at the root, patches operating systems and apps on a schedule, and advises on what to replace and when. Remote sessions happen only with your consent.

## Key terms
- **Task Manager**: The Windows tool (Ctrl + Shift + Esc) that lists running processes with their processor, memory, disk and network use, the apps that start at sign-in, and performance graphs.
- **Resource Monitor**: A more detailed Windows monitor, opened with resmon or perfmon /res, that can rank processes by their average processor use over time rather than at one moment.
- **Startup impact**: Task Manager's rating of how much processor time and disk activity an app used when it started at sign-in. High means more than 1 second of CPU time or more than 3 MB of disk activity.
- **Disk latency**: How long each read or write takes to complete. Microsoft's performance guidance treats under 15 ms as healthy and sustained values above 25 ms as a warning.
- **Commit charge**: The memory Windows has promised to programs. It cannot exceed the commit limit, physical RAM plus all page files; at the limit, programs can freeze or crash.
- **Thermal throttling**: A processor lowering its clock speed to protect itself when its temperature goes above its maximum, so the PC runs slower until it cools down.
- **Reliability Monitor**: A Windows tool (perfmon /rel) that plots a daily System Stability Index from 1 to 10 next to the installs and failures recorded on each day.
- **Event Viewer**: The Windows console for the event logs. The System and Application logs record errors and warnings from Windows, drivers and programs, with the time each happened.
- **Clean boot**: Starting Windows with only essential drivers and startup programs, to find out whether third-party software is causing a problem, then narrowing it down by halves.
- **Microsoft Defender offline scan**: A Windows Security scan that runs after a restart without loading Windows, so persistent malware has a harder time hiding or defending itself.

## Common questions

### Why is my computer suddenly so slow?

A sudden slowdown often follows a change: an update, a new driver or app, a failing drive or malware. Open Reliability Monitor (perfmon /rel) and look at what was installed on the day the stability line dropped, then check Task Manager for the process using the most CPU, memory or disk right now.

### How do I fix 100% disk usage in Windows 11?

Sort Task Manager's Processes page by Disk to see what is using the drive. Search indexing and antivirus scans finish on their own, and heavy paging means memory is short. If nothing explains it, check Drive health under Settings > System > Storage > Advanced storage settings > Disks & volumes, and back up first if it shows a warning.

### Why does Windows 11 take so long to start up?

A common cause is too many apps starting with Windows. On Task Manager's Startup apps page, disable the High-impact ones you do not need at sign-in, then restart and compare. If that does not help, a clean boot shows whether a third-party service is responsible; a longer start-up can also be a sign of a failing drive.

### Will restarting fix a slow computer?

Often, for a while. Microsoft recommends closing the apps and browser tabs you are not using and restarting if performance does not improve. If the slowness comes back, the restart only cleared the symptom, and Task Manager is the place to find the cause.

### Can a virus make my computer slow?

Yes. Malware can consume processor and disk resources like any other program. Run a Quick scan in Windows Security, and a Microsoft Defender offline scan if you still suspect something, because it scans before Windows loads.

### When is a slow computer not worth fixing?

When the hardware is the limit. Microsoft notes that older PCs with outdated hardware may not see significant improvements from software fixes. If memory stays at its commit limit with your normal workload, or the drive reports health warnings, new parts or a new PC is the real fix.

## Sources
1. [Windows 11 release information](https://learn.microsoft.com/en-us/windows/release-health/windows11-release-information), Microsoft Learn
2. [Tips to improve PC performance in Windows](https://support.microsoft.com/en-us/windows/experience/performance-optimization/tips-to-improve-pc-performance-in-windows), Microsoft Support
3. [Guidance for troubleshooting high CPU usage](https://learn.microsoft.com/en-us/troubleshoot/windows-server/performance/troubleshoot-high-cpu-usage-guidance), Microsoft Learn
4. [perfmon](https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/perfmon), Microsoft Learn
5. [Configure Startup applications in Windows](https://support.microsoft.com/en-us/windows/experience/startup-boot/configure-startup-applications-in-windows), Microsoft Support
6. [How to perform a clean boot in Windows](https://support.microsoft.com/en-us/windows/experience/startup-boot/how-to-perform-a-clean-boot-in-windows), Microsoft Support
7. [Troubleshoot performance problems in Windows](https://learn.microsoft.com/en-us/troubleshoot/windows-server/performance/troubleshoot-performance-problems-in-windows), Microsoft Learn
8. [Get-Counter](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.diagnostics/get-counter), Microsoft Learn
9. [Search indexing in Windows](https://support.microsoft.com/en-us/windows/experience/performance-optimization/search-indexing-in-windows), Microsoft Support
10. [Virus and threat protection in the Windows Security app](https://support.microsoft.com/en-us/windows/security/threat-malware-protection/virus-and-threat-protection-in-the-windows-security-app), Microsoft Support
11. [Introduction to the page file](https://learn.microsoft.com/en-us/troubleshoot/windows-client/performance/introduction-to-the-page-file), Microsoft Learn
12. [What to do about a critical warning for a storage device](https://support.microsoft.com/en-us/windows/experience/storage-filemanagement/what-to-do-about-a-critical-warning-for-a-storage-device), Microsoft Support
13. [Get-PhysicalDisk](https://learn.microsoft.com/en-us/powershell/module/storage/get-physicaldisk), Microsoft Learn
14. [Get-StorageReliabilityCounter](https://learn.microsoft.com/en-us/powershell/module/storage/get-storagereliabilitycounter), Microsoft Learn
15. [Learn about performance features in Microsoft Edge](https://support.microsoft.com/en-us/edge/learn-about-performance-features-in-microsoft-edge), Microsoft Support
16. [Speed up Google Chrome](https://support.google.com/chrome/answer/1385029), Google Chrome Help
17. [Personalize Chrome performance](https://support.google.com/chrome/answer/12929150), Google Chrome Help
18. [What to do if Microsoft Edge isn't working](https://support.microsoft.com/en-us/edge/what-to-do-if-microsoft-edge-isn-t-working), Microsoft Support
19. [Fix videos & games that won't play](https://support.google.com/chrome/answer/6138475), Google Chrome Help
20. [HardwareAccelerationModeEnabled (Microsoft Edge policy)](https://learn.microsoft.com/en-us/deployedge/microsoft-edge-policies/hardwareaccelerationmodeenabled), Microsoft Learn
21. [Chrome Enterprise policy list: HardwareAccelerationModeEnabled](https://chromeenterprise.google/policies/#HardwareAccelerationModeEnabled), Google Chrome Enterprise
22. [Reset Chrome settings to default](https://support.google.com/chrome/answer/3296214), Google Chrome Help
23. [Fix Wi-Fi connection issues in Windows](https://support.microsoft.com/en-us/windows/experience/connectivity-networking/fix-wi-fi-connection-issues-in-windows), Microsoft Support
24. [How to Use Windows Reliability Monitor to Identify Software Issues](https://www.dell.com/support/kbdoc/en-us/000178177/how-to-use-windows-reliability-monitor-to-identify-software-issues), Dell Technologies
25. [Understanding the System Stability Index](https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-r2-and-2008/cc749032%28v=ws.10%29), Microsoft Learn
26. [Use Reliability Monitor to Troubleshoot](https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-r2-and-2008/cc749583%28v=ws.10%29), Microsoft Learn
27. [Windows startup issues troubleshooting](https://learn.microsoft.com/en-us/troubleshoot/windows-client/performance/windows-boot-issues-troubleshooting), Microsoft Learn
28. [Windows Update: FAQ](https://support.microsoft.com/en-us/windows/deployment/updates-lifecycle/windows-update-faq), Microsoft Support
29. [Update drivers through Device Manager in Windows](https://support.microsoft.com/en-us/windows/update-drivers-through-device-manager-in-windows-ec62f46c-ff14-c91d-eead-d7126dc1f7b6), Microsoft Support
30. [Recovery options in Windows](https://support.microsoft.com/en-us/windows/experience/backup-recovery/recovery-options-in-windows), Microsoft Support
31. [What Is Throttling and How Can It Be Resolved?](https://www.intel.com/content/www/us/en/support/articles/000088048/processors.html), Intel
32. [Change the power mode for your Windows PC](https://support.microsoft.com/en-us/windows/change-the-power-mode-for-your-windows-pc-c2aff038-22c9-f46d-5ca0-78696fdf2de8), Microsoft Support
33. [Power settings in Windows 11](https://support.microsoft.com/en-us/windows/experience/power-battery/power-settings-in-windows-11), Microsoft Support
34. [View information about Mac processes in Activity Monitor](https://support.apple.com/guide/activity-monitor/view-information-about-processes-actmntr1001/mac), Apple Support
35. [Check if your Mac needs more RAM in Activity Monitor](https://support.apple.com/guide/activity-monitor/check-if-your-mac-needs-more-ram-actmntr34865/mac), Apple Support