C drive is full. What should I delete to clean up C drive safely?

When your C drive is full (especially with only 6GB free), certain actions can lead to catastrophic errors. When you're desperate for space, it's tempting to hunt for the biggest files and delete them. But if you delete the wrong system file—even one you think is "just a temp file"—Windows might not start next time.

1. Don't Let Windows Update Run or Restart for Updates
Windows Update needs breathing room—like 10–20GB—to unpack and install updates.
If it starts with only a few GB free, it’ll fail halfway through and leave your system in update limbo: not the old version, not the new version, just broken.

2. Don't Force a Shutdown or Restart While Things Are Hanging
When the drive is full, everything slows down—programs freeze, Explorer stops responding. 
If you hold the power button to force a shutdown, you risk cutting off Windows while it's writing something important. That's how you corrupt system files, user profiles, or the registry.

3. Don't Run "Cleaner" Apps Aggressively
Apps like Third-party software promise to free up space, but when the drive is critically low, they can remove files Windows is actively using or delete restore points you might need.

4. Don't Mess with Virtual Memory Settings
Yes, you can move the pagefile to another drive—but don't disable it entirely.
Windows uses it as emergency RAM. Without it, programs will crash, and you could get memory errors that freeze the whole system.

The C disk is full is not a difficult problem, but it should be noted that: Always back up important data before deleting large files or performing cleanup operations, especially if you're not sure about their importance. Some cache or temporary files may be needed for ongoing processes or applications. Deleting them indiscriminately might cause apps to malfunction or lose session data. Do not manually delete files from application directories unless the program is uninstalled properly. This can leave residual files or corrupt the application.