A slow Windows computer can usually be fixed with 10 safe steps, done in order from least to most risky: back up and restart, update, scan for viruses, find resource-hungry apps, turn off startup apps, clean up the disk, then adjust performance options. If you have done all of this and it is still slow, it may be time to upgrade the hardware.
This routine is based on Microsoft's public guidance on improving Windows performance and freeing up disk space. For Mac, read the separate article on a Mac with full storage or running slowly (coming November 13, 2026).
What to do before cleaning up?
Step 1: Back up and restart. Copy important files to an external drive or a cloud storage service. The rule of keeping several copies in several places is covered in the article on the 3-2-1 backup rule. Then close any open apps and choose Start, Power, Restart. Microsoft lists restarting and closing unused apps right in its tips, because a machine that has been running for a long time tends to accumulate processes.
Step 2: Update. Go to Settings, Windows Update, Check for updates and install optional updates such as drivers too. Updates both patch security holes and can fix performance bugs.
Step 3: Scan for viruses. Open Windows Security, choose Virus & threat protection, then Quick scan. Malware is one cause of unusual slowness.
How do I find out what is slowing the computer down?
Step 4: Check Task Manager. Press Ctrl+Shift+Esc and open the Processes tab to see which apps use the most CPU, memory or disk. Microsoft advises closing unused apps here, and also checking the Performance and Startup apps tabs to assess usage.
Step 5: Turn off startup apps. In Task Manager, open the Startup apps tab and disable apps you don't need to run automatically at boot. Only disable things you recognize; leave system items and antivirus software alone.
Step 6: Uninstall unused apps. Go to Settings, Apps, Installed apps and remove apps you no longer use. This also recovers disk space.
How to clean up the disk safely?
Step 7: Free up disk space. Microsoft suggests using Storage Sense, a tool that automatically deletes temporary files and Recycle Bin contents, or checking Temporary files in Storage. On Windows 11, Cleanup recommendations groups items into temporary files, large or unused files, files already synced to the cloud, and unused apps, each with its own Clean up button. Details on what to delete and what to keep are in the article on freeing up Windows disk space (coming November 4, 2026).
Step 8: Turn off background apps and extra notifications. For apps that don't need to run in the background, set background permissions to Never. Also turn off notifications from apps you don't need to reduce background tasks.
Should I adjust visual effects and power mode?
Step 9: Adjust visual effects and power mode. Microsoft lets you choose "Adjust for best performance" in the visual effects options, which reduces animations. You can also set Power mode to Best performance, but this uses more power, so a laptop battery drains faster. If you often use a laptop unplugged, think it over.
Step 10: Optimize the drive and consider an upgrade. Open Defragment and Optimize Drives, select a drive and click Optimize. Microsoft also mentions the PC Manager app, which helps with cleanup, startup management and optimization. Also, an older machine may improve only a little, so upgrading is often the longer-lasting solution.
When should an old computer be replaced instead of rescued?
Signs to consider upgrading or replacing the machine: it takes more than a few minutes to boot, even an office app stutters, the disk is full despite cleanup, or it no longer receives security updates. For old office machines after Windows 10 reaches end of support, read Windows 10 end of support: options for old office computers and the decision table for office machines. Some older machines run better with a lightweight operating system.
In This Series
This article is the pillar of the "Cleaning up and speeding up your computer" series. Detailed articles:
- Freeing up Windows disk space: what to delete and what to leave alone (coming November 4, 2026) (November 4, 2026)
- Mac with full storage or running slowly: steps following Apple's guidance (coming November 13, 2026) (November 13, 2026)
- Android phone with full storage: clearing photos, apps and cloud storage (coming November 22, 2026) (November 22, 2026)
- iPhone with full storage: back up first, then clean up, to avoid losing data (coming December 1, 2026) (December 1, 2026)
- Slow, heavy browser: clean up extensions and cookies and turn on updates (coming December 10, 2026) (December 10, 2026)
- Windows and browser shortcuts that save half an hour a day (coming December 19, 2026) (December 19, 2026)
FAQ
What should I do first when my computer is slow?
Restart the computer, update Windows, then open Task Manager to see which apps are using the most resources. These three steps are safe and cause no data loss.
Should I install third-party cleaner software?
Not necessary in most cases. Windows already has Storage Sense, Task Manager and Windows Security. Unfamiliar software may overpromise in its advertising or contain malware.
What if an old computer is still slow after cleanup?
Microsoft notes that an old machine may improve only a little, and upgrading the hardware or replacing the machine may be the longer-lasting solution. Adding RAM or replacing the hard drive with an SSD is worth considering, and it is best to have a knowledgeable person check first.
Will cleanup cause data loss?
It can, if you delete the wrong things. Back up important files first, and only delete items Windows suggests, such as temporary files. Once the Recycle Bin is emptied, files cannot be recovered.
For reference only: content compiled from the 3 official sources listed below, as of the time of research (10/2026). Please recheck on the official sites before making a decision. Updated 26/10/26.
Reference sources
- Microsoft — Tips to improve PC performance in Windows: https://support.microsoft.com/windows/tips-to-improve-pc-performance-in-windows-b3b3ef5b-5953-fb6a-2528-4bbed82fba96
- Microsoft — Free up drive space in Windows: https://support.microsoft.com/windows/free-up-drive-space-in-windows-85529ccb-c365-490d-b548-831022bc9b32
- Apple — What to do if your Mac runs slow: https://support.apple.com/guide/mac-help/what-to-do-if-your-mac-runs-slow-mh35827/mac
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FAQ
What should I do first when my computer is slow?
Restart the computer, update Windows, then open Task Manager to see which apps are using the most resources. These three steps are safe and cause no data loss.
Should I install third-party cleaner software?
Not necessary in most cases. Windows already has Storage Sense, Task Manager and Windows Security. Unfamiliar software may overpromise in its advertising or contain malware.
What if an old computer is still slow after cleanup?
Microsoft notes that an old machine may improve only a little, and upgrading the hardware or replacing the machine may be the longer-lasting solution. Adding RAM or replacing the hard drive with an SSD is worth considering, and it is best to have a knowledgeable person check first.
Will cleanup cause data loss?
It can, if you delete the wrong things. Back up important files first, and only delete items Windows suggests, such as temporary files. Once the Recycle Bin is emptied, files cannot be recovered.
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