I totally agree with the OP here.
Grimefighter is nagware.
It pops up on my Vista machine, tells me it has grime.
But it wont tell me what the grime is.
For all I know this grime could just be tempory files so if I payed they could just end up cleaning temporary files which is something I could do my self for free with tools already built in to Windows.
Seriously Avast used to be a brilliant antivirus company with a good reputation. Now they are starting underhanded tactics like tricking people to install google chrome, google toolbar and dropbox with those annoying optional extras that are ticked to install by default.
On top of that they have this grime fighter which tells you you have grime but doesn't tell you what it is. Which means if you're gullible you could end up paying for a program that just deleted temporary files.