Did you get rid of ALL the temp files? I'd suggest using CCleaner, although, 25GB is pretty damn big for just temp files. The other suggestion is to turn off hiding system and other hidden files, and then go into the %SYSTEM% directory and remove all the MS update installation directories. They are in sub-directories and have a name format of $NtUninstallKBnnnnnn$ and are all hidden by default. I'd suggest moving them to a portable HD, and not merely deleting them, as you may need them in the future.
If those suggestion doesn't work, I'd suggest getting a utility that can tell you the size of the directories, and track the problem down from there. Sometimes a typo or other mistake can make damn strange things to the files structure. I've had some clients manage to drag folders around to that they up recursive directories. In one case it was so recursive they filled up a 200GB backup drive.



