AFAIK disk cleanup does not clear (delete) old files, it just compresses them.
So, I may have old files from 3 years ago, files that haven't been used for that long and that I do not need, and they would still be on my hard drive in compressed form. Is that right? This isn't making a lot of sense to me. Surely, there's a way to stop Compress Old Files from just continuing to accumulate old files and keep them in compressed form forever.
When I run Disk Cleanup, it shows no drive space being consumed by Compress Old Files. I click on Options and see that it's set at 50 days (a default setting, I believe, since I don't recall ever setting that). So, the 0 MB shown next to Compress Old Files means I have no files that have not been used in over 50 days, right? That seems hard to believe. But, indeed, I guess it indicates I either have no files unused for over 50 days, or I've run Disk Cleanup at frequent enought intervals to remove unused files less than 50 days old.
So, anyway, Compress Old Files appears to be the oddball in the Disk Cleanup panel; all the others do, in fact, remove files from the hard drive while Compress Old Files compresses old files and removes nothing.