First, check whether there are any important documents on your C drive. If so, put it in another drive first. If you are not clear, you can use the 360 tool to find large files.

Then clean up the unused things on other disks. If the system is still a card, check the fragments of your C disk system to see if it needs sorting. Right-click on drive C and find the tool-defragment.

If not, you can redo the system and format drive C directly. Everything is clean! ! !