CC does not clean every file used when you use an application such as Firefox. There are logs, swap files, all the stuff that Windows thinks it needs to live and breathe. CC will (should) clean all the files it analyses. If you think that CC isn't cleaning something it should then post the file names here and we'll try to sort it.
I have ran two crap cleaners your side by side with another wich is only part of a bigger program and not its main feature.
I ran CCleaner and wiped out a 180MB'ish of all sorts... Then I ran the other I mean straight after another 121 temp files were wiped releasing an extra 96MB...
I will try and find a log and post it here.....
Ah also the sqm files in xp are not getting cleaned those are messenger something or others arent they? C:/ hidden files? yea I noticed that dont knwo why but in vista its workig ok on that front.