I had a worse problem than the previous user. My computer (HP Pavillion w/Vista) crashed while running the Wipe free space (it crashed for another reason). It was wiping 288 GB of free space, when I started back I re-ran the CCcleaner, wipe free space, and it was wiping only 70 GB of free space!! Not to worry, I've had this problem before with Cleaners. I simply found a BIG BIG many GB file (288-70) GB on the root directory of C:\
DELETING that big file got back my 288 GB...
I hope this helps...