1. Check for any potential system error messages that may be displayed on the screen.

2. Check the Recycle Bin for files and folders that may have been deleted.

3. Delete old temporary files from the computer.

4. Check for any suspicious-looking software that may have been installed recently.

5. Die something virus scan to detect any malicious programs.

6. Uninstall any suspicious software.

7. If the files are still missing, consider backing up data on an external drive.