QUOTE (thoste @ Nov 3 2009, 03:16 PM)

Instead of letting the user fiddle around in some nested, hidden Group Policy editors or Registry branches
CCleaner should offer a simple checkbox which let it run at shutdown time.
It already offers shutdown after a fashion ... as in "run then shutdown". I.e. it
triggers a shutdown on completion rather than
responds to shutdown events. Don't forget that ccleaner requires a user context, so it has to be done before logoff (as per your original post). It's no use having it in the shutdown script because the context has gone.
Also, not all OS versions (e.g. XP Home) support GP and I don't think (though I've not tried) it's as straightforward as just manipulating the reg keys in those cases.