Windows has a lot of TEMP folders. Just search for 'TEMP' and numerous folders wil appear. The environment variables hold the paths to TEMP-folders for both the user and system. When these locations are changed (IE - the environment variables are changed), then CCleaner will scan the new locations as it should. But changing the location doesn't clear out the 'old' folders. So there could be quite some left-overs after a change. To get rid of that junk, it would be nice if CCleaner scanned all possible default temp-folders.
Simon