Disk Clean UP

I'm probably putting this in the wrong forum, but.....
Everytime I've tried to run my disk clean-up over the past two days my computer has shut down. I don't know whether it's working too hard or what, but it's driving me crazy. Any suggestions? If I had to guess, I'd say there are too many files to compress. I've been using CCleaner, but this time decided to try the Disk Clean-up on the computer. Surprise - there were over 2,000,000 files to compress. It must do something before the computer shuts off, because I'm down to 600,000.