Back up important files
Empty the Recycle Bin or Trash
Delete temporary files
Uninstall unused programs
Remove duplicate files
Clear browser cache and downloads
Move large files to external storage or cloud storage
Run Disk Cleanup or a similar system tool
Delete old system restore points
Scan for and remove malware
Defragment the drive if it is an HDD
Check disk usage and remove unnecessary files
Clean out old email attachments and media files
Remove unused user accounts and profiles
Restart the computer after cleanup