The drive C bar in File Explorer has turned red, Windows Update keeps failing, and your PC feels slower than usual. When the system drive fills up, Windows doesn’t have room for updates, temporary files or virtual memory. Here’s how to free up space on drive C safely, starting with the easy wins and moving to bigger changes, without deleting anything you’ll regret.
Step 1: See what’s using the space
Open Settings > System > Storage. Windows shows a breakdown by category: Apps & features, Temporary files, Documents, Pictures, Videos and so on. Click Show more categories to see everything. This tells you where to focus instead of guessing.
Step 2: Clean temporary files and cleanup recommendations
- In Settings > System > Storage, click Temporary files.
- Wait for the scan, then review the list. Items like Windows Update Cleanup, Delivery Optimization Files, Temporary files and Thumbnails are safe to remove.
- Be careful with Downloads. If it’s checked, Windows will delete everything in your Downloads folder. Uncheck it unless you’ve already looked through that folder.
- Click Remove files.
Also open Cleanup recommendations on the same Storage page. It suggests large or unused files, files already backed up to OneDrive and apps you rarely open. Review each suggestion before removing it.
Prefer the classic tool?
Search for Disk Cleanup in the Start menu, select drive C, then click Clean up system files. It offers similar options and works on Windows 10 and 11.
Step 3: Empty the Recycle Bin
Deleted files stay in the Recycle Bin and keep taking space until you empty it. Right-click the Recycle Bin on the desktop and choose Empty Recycle Bin, after a quick look to make sure there’s nothing you want back.
Step 4: Uninstall apps and games you don’t use
Go to Settings > Apps > Installed apps, then sort by Size. Games and creative suites can take tens of gigabytes each. Uninstall anything you haven’t used in months. You can always reinstall it later.
Look out for trial software that came with your PC, like antivirus trials. If you’re unsure whether you need a separate antivirus, our guide to the best free antivirus for Windows explains why many people can rely on the built-in Microsoft Defender.
Step 5: Move big personal files off drive C
Videos, photo libraries and old project files often take the most space. Options:
- Another drive: if your PC has a second drive (D or E), move large folders there.
- External drive: archive old videos and photos you don’t open often.
- Cloud storage: with OneDrive, Google Drive or similar, turn on the option to keep files online-only. In OneDrive, right-click a folder and choose Free up space. The files stay visible but download only when you open them.
You can also change where new files are saved: Settings > System > Storage > Advanced storage settings > Where new content is saved.
Step 6: Turn on Storage Sense
Storage Sense cleans up automatically so you don’t have to repeat these steps every month.
- Go to Settings > System > Storage.
- Turn on Storage Sense and click it to configure.
- Set how often it runs, and choose how long files stay in the Recycle Bin and Downloads before being deleted. For Downloads, “Never” is the safest choice if you tend to keep important files there.
Step 7: Remove an old Windows installation
After a major Windows upgrade, a folder called Windows.old keeps your previous version so you can roll back. It can be large. Once you’re happy with the update (Windows usually removes it on its own after about 10 days), you can delete it through Temporary files by checking Previous Windows installation(s). After that, you can’t go back to the previous version.
Step 8: Optional advanced savings
Turn off hibernation
The hibernation file (hiberfil.sys) can take several gigabytes. If you never use hibernate, open Command Prompt as administrator and run:
powercfg /h off
This also disables Fast Startup. To turn it back on, run powercfg /h on.
Check for large forgotten files
In File Explorer, open drive C, type size:gigantic in the search box and press Enter. It lists files larger than 4 GB. Look for old virtual machine files, video exports or installer images you no longer need.
What not to delete
- Anything inside C:Windows, especially the WinSxS folder. Use the cleanup tools instead of deleting by hand.
- pagefile.sys, which Windows uses as virtual memory.
- Program Files folders. Uninstall apps through Settings so they’re removed properly.
- Random “PC cleaner” or “registry booster” programs promising huge savings. Windows’ own tools are safer.
A full drive is one common reason for slowdowns, but not the only one. Our guide on why your computer is so slow covers the rest. And if updates were failing because of low space, see how to fix a stuck Windows Update.
FAQ
How much free space should drive C have?
A common rule of thumb is to keep at least 15 to 20 percent of the drive free. That leaves room for updates, temporary files and virtual memory, and helps Windows run smoothly.
Is it safe to delete temporary files in Windows?
Yes, when you use Windows’ Temporary files tool or Disk Cleanup. Just watch the Downloads checkbox, because it deletes your personal downloads, not system junk.
Why is drive C full when I haven’t saved much?
Updates, temporary files, the hibernation file, game installs and cloud sync caches add up quietly. The Storage page in Settings shows which category is to blame.
Can I move programs from C to D?
Some Microsoft Store apps can be moved through Settings > Apps > Installed apps > Move. Traditional desktop programs should be uninstalled and reinstalled to the other drive rather than copied.
