I always did clean ups manually, so I can't help you with software.
Is there a way to search for files bigger than x? Perhaps you would see files that are huge and that you don't need. I used to keep all zip archives when downloading something . that's not necessarily a great idea...
Do you save any sort of backup to your C drive? If so, there might be sets of old files that a re copies or outdated.
Do you save photos to your C drive? If you do like me, you might save lots of same motif pictures planning to sort out the better copies to keep later - but never getting to it. I normally delete 50% of my pictures once I get to it.
Saving any media files on your drive? Videos make for huge files, maybe delete or move to an external drive?
Also in TS4 there might be old saves that you can delete. Deleting them will also make the game run smoother.
If you often take pictures in game, your Screenshots folder might be about to explode. Move the entire folder to a USB storage. Also helps on game performance. Same for TS4 videos.
