While writing my previous suggestion, I thought of another useful area the CCleaner could clean up crap from, that that would be the oft' overlooked environment variables.
For the uninitiated, you can view these by selecting System from the control panel (or right-click on My Computer and select Properties), go to the Advanced tab, and click the Environment Variables button near the bottom.
At the very least, removing non-existent folders from the "Path" variable would be handy.
You could also possibly do similar for other well known path variables such as CLASSPATH.
Possibly also verify other common variables point to valid files or folders, such as JAVA_HOME, TEMP, TMP, HOME, ComSpec and windir to name a few.
What do you think?