DavidR
6
See - Uninstall possible remnants of previously installed AVs, http://singularlabs.com/uninstallers/security-software/, this has a collection of manufactures removal tools, so that should remove any remnants, registry, etc.
Item [02] AVG AV > Info > Tool (32bit) - Tool (64 bit) in the list of uninstallers, ensure that you get the correct one for your OS/version of A V G (32bit or 64bit uninstaller).