If you turn on the backup of the system, it will probably take 7G according to your situation!
Delete previous restore points:
Click Start-Programs (All Programs)-Accessories-System Tools-Disk Cleaning.
Click More Options, click Cleanup under System Restore and Shadow Copy, and then click Delete.
Check whether the download folder of the downloaded software is on drive C. Have I put too many things on the document and desktop?
Cclean again.