I've been using ccleaner for a few years; it has received many excellent reviews. I use the registry cleaner and the cleaner which cleans up all the junk left behind in temp space, internet explorer temp files,.... I used it for the first time when my husband's desktop for some reason showed no available disk space and was acting crazy. I thought I would have to reinstall. I was amazed when ccleaner made available gigabytes and solved the problem. (This is the only time I have had extreme results like this but I continue to use it because it seems to recover more space than the Windows tools.)
CNET which I trust for reviews still lists it as free.
http://download.cnet.com/ccleaner/
I don't want to try to download it again to check to see what the problem is. Some of the free programs have an updated version that you have to pay for. Could this be the case?