I'm running Windows 7 Home 64 bit, I think I downloaded CCleaner from CNet Downloads quite awhile back. I've used it for years on different computers and multiple times on this one with no problems. I first did a standard clean and then I did the registry clean. When I immediately saw a problem, I looked to see how to undo and saw it said to merge the backup reg file, which I did, but nothing changed. I then did a system restore, but still nothing.