I use it daily. Just run it (doesn't have to be installed) and click Select All from the bottom of the list of remove options and click Empty Selected button. It also empties the windows\prefetch folder prashant_304 mentions. I like that it gets so many places in one fell swoop.
All of this is suggested to you if you indeed are out of space on the C: drive. If you mean that the available space on the C: is being misreported as full, then poswt back to us here.