Why Is My Computer So Slow? How to Find the Cause and Fix It

A slow computer almost always has one of a few causes: too many apps launching at startup, a disk or processor that is maxed out, memory that is full, a nearly full drive, pending updates, malware, or an old spinning hard drive. The fastest way to find out which one is to restart, then open Task Manager and look at what is running at 100%. The steps below work on Windows 11 and Windows 10, and they start with the free fixes.

Note: Microsoft ended support for Windows 10 on October 14, 2025. The steps still work, but an unsupported PC no longer gets security fixes, so moving to Windows 11 (or a newer PC) is the long-term answer for an old Windows 10 machine.

What makes a computer slow

Most slowdowns fall into one of these buckets:

• Startup apps. Every app that launches with Windows takes CPU, memory and disk time before you can do anything.
• A busy resource. One process using most of the CPU, memory or disk makes everything else wait.
• Low free space. Windows needs room on the system drive for temporary files and the page file.
• Updates and drivers. Updates installing in the background can slow things down, and outdated drivers can cause problems of their own.
• Malware. Malicious software runs in the background and eats resources.
• An old hard disk drive (HDD). Hard drives use spinning platters and read/write heads, while SSDs use flash memory with no moving parts. An SSD is much faster at booting and loading apps.

Step 1: Restart and close what you don’t need

It sounds too simple, but a restart clears out apps that have piled up and finishes pending updates.

1. Save your work and close apps and browser tabs you aren’t using.
2. Select Start > Power > Restart.
3. After the restart, give Windows a minute or two to finish loading before you judge the speed.

Step 2: Find the bottleneck in Task Manager

Task Manager shows exactly what is using your PC’s resources.

1. Press Ctrl+Shift+Esc to open Task Manager.
2. On the Processes tab, select the CPU, Memory and Disk column headers one at a time to sort by the heaviest users.
3. Open the Performance tab to see overall CPU, memory and disk use over time.
4. If an app you don’t need is at the top, select it and choose End task.

Here is how to read what you see:

What Task Manager shows	Where to go next
One app uses most of the CPU	Close or update that app, or remove it if you don’t use it
Memory is nearly full all the time	Close apps, disable startup apps, and consider more RAM
Disk sits near 100%	Check free space, scan for malware, and see whether the drive is an HDD
A Windows service is busy	See what Service Host: SysMain (SuperFetch) does or check if search indexing is running

Tip: Don’t end processes you don’t recognize just because they use resources. Many belong to Windows. Search the exact process name first.

Step 3: Turn off startup apps

Apps that start with Windows are one of the most common reasons a PC feels slow right after you sign in.

1. Press Ctrl+Shift+Esc to open Task Manager.
2. Select Startup apps.
3. Check the Startup impact column to see which apps slow down startup the most.
4. Right-click an app you don’t need right away and select Disable.

You can also do this in Start > Settings > Apps > Startup by switching each app’s toggle off. Disabling a startup app doesn’t uninstall it. You can still open it whenever you want.

Step 4: Free up disk space

Microsoft recommends keeping roughly 10 to 15 percent of the drive free. When the system drive gets close to full, Windows has less room to work.

Run Storage Sense:

• Windows 11: Select Start > Settings > System > Storage > Storage Sense, then Run Storage Sense now.
• Windows 10: Select Start > Settings > System > Storage, turn on Storage Sense, then use Configure Storage Sense or run it now and select Clean now.

Delete temporary files (Windows 10 and 11):

1. Go to Start > Settings > System > Storage > Temporary files.
2. Check the types of files you want to remove.
3. Select Remove files.

Important: Read each category before you check it. Removed files are deleted, so leave unchecked anything you might still need.

You can also search for Disk Cleanup, open it and select the drive to clean.

Step 5: Scan for malware

Malware often shows up as a PC that is slow for no obvious reason.

• Windows 11: Select Start > Settings > Privacy & security > Windows Security > Virus & threat protection, then Quick scan.
• Windows 10: Select Start > Settings > Update & Security > Windows Security > Virus & threat protection, then under Current threats select Quick scan.

If the scan finds something, follow the steps Windows Security gives you and restart.

Step 6: Install Windows updates and optional drivers

Updates include performance and reliability fixes, and optional updates can include newer drivers.

• Windows 11: Select Start > Settings > Windows Update > Check for updates. For drivers, go to Windows Update > Advanced options > Optional updates.
• Windows 10: Select Start > Settings > Update & Security > Windows Update > Check for updates. If you see View optional updates, open it and select Download & install.

Restart when Windows asks you to. If updates fail with an access-denied code, see our fix for Windows Update error 0x80070005.

Step 7: Remove apps you don’t use and limit background apps

Uninstall unused apps:

• Windows 11: Start > Settings > Apps > Installed apps, select More options (…) next to the app, then Uninstall.
• Windows 10: Start > Settings > Apps > Apps & features, select the app, then Uninstall.

Stop apps running in the background:

• Windows 11: In Installed apps, select More options (…) > Advanced options. Under Background app permissions, set Let this app run in the background to Never.
• Windows 10: Go to Start > Settings > Privacy > Background apps and turn off the apps you don’t need.

Step 8: Change the power mode and visual effects

Power mode:

• Windows 11: Start > Settings > System > Power & battery, then set Power mode to Best performance.
• Windows 10: Start > Settings > System > Power & sleep > Additional power settings, then pick High performance (select Show additional plans if you don’t see it).

On a laptop this drains the battery faster, so you may want to switch back when you’re unplugged.

Visual effects (Windows 10 and 11):

1. Search for Adjust the appearance and performance of Windows and open it.
2. On the Visual Effects tab, select Adjust for best performance.
3. Select OK.

Windows will look plainer. If you miss a specific effect, such as smooth fonts, you can check it again in the same list.

Step 9: Optimize your drives

Windows defragments hard drives and sends a “trim” to SSDs, and by default it does this once a week.

1. Search for defrag and open Defragment and Optimize Drives.
2. Select your drive.
3. Select Optimize.

Under Scheduled optimization, select Change settings if you want to check that the weekly schedule is turned on.

Check if you have a hard drive or an SSD

If your PC still has a spinning hard drive, that is often the biggest bottleneck of all. To check:

1. Right-click Start and open Terminal (Windows 11) or Windows PowerShell (Windows 10).
2. Run:

Get-PhysicalDisk | Select-Object FriendlyName, MediaType, HealthStatus

This lists each physical drive with its media type: HDD, SSD or Unspecified. It also shows a basic health status.

If your Windows drive is an HDD and Task Manager often shows the disk at 100%, replacing it with an SSD is usually the upgrade that makes the most difference. SSDs have no moving parts and load Windows and apps much faster than hard drives, though they cost more per gigabyte. Check your PC’s manual or the manufacturer’s support page first to see which drive type fits (2.5-inch SATA or M.2), then check SSD prices on Amazon.

Important: Back up your files before you swap a drive. Moving Windows to a new drive means either cloning the old drive or reinstalling Windows, and both can lose data if something goes wrong.

Why is my computer so slow all of a sudden?

If your PC was fine yesterday and is slow today, think about what changed:

• An update is installing. Check Windows Update for a pending restart.
• A new app was installed. It may have added itself to startup apps.
• The drive filled up. Large downloads or a game install can push the system drive past the 10-15% free mark.
• Search is reindexing. After many new files are added or after an upgrade, the Windows Search indexer can spend hours catching up. Microsoft’s guidance is to leave the PC on and plugged in so indexing can finish. If search itself stops working, use our guide to the Windows search bar not working.
• Malware. Run the Quick scan from Step 5.

If the slowdown comes with crashes or blue screens, the cause may be hardware. A MEMORY_MANAGEMENT stop code, for example, points at RAM, drivers or the disk. See our memory management blue screen fix.

If it still doesn’t work

If you’ve worked through every step and your PC is still slow:

• Check the drive’s health. If Get-PhysicalDisk reports anything other than Healthy, back up your files right away and plan to replace the drive.
• Look at your hardware age. Microsoft notes that older PCs may see little improvement from these tweaks, and upgrading may be the better long-term fix.
• Try a clean user account. If a new Windows user account is fast, the problem is in your profile or the apps that start with it.
• Get help. If you’re at work, contact your IT team. At home, a local repair shop can test the drive and memory for you. For more ways to keep a Windows 11 PC fast, see how to speed up Windows 11, and for other hardware and Windows problems, browse our computer repair tips.