I've had aggravations with AVG 10(free) mail scanner not allowing rich text emails to be sent causing complaints that the message has non-smtp characters in it. Having failed to find a solution for that I decided to change from AVG to another antivirus programme.
I downloaded AVG's uninstall programme from thir website and ran it. It seemed to be a bit confused that i had AVG installed in a non-default location but it eventually ran ok.
Subsequently, I checked for detritus and found to my surprise that I had 164 files in various places and 157 registry entries (using Regseeker) that had not been removed.
I don't know if these leftovers were ignored because of the non-default installation location or if the uninstaller just isn't that thorough, but anyone using the AVG proprietary uninstaller should be aware that there may well be a whole raft of left-overs that will need to be removed manuallly.