Try downloading and running the AVG removal tool and then try doing your new download again.
I am operating XP with service pac 3. Have used AVG free versions since 2009 with no problem. Attempted to update to 2013 free version, ended up with trial by mistake. Attempted to remove and go to free. Froze for over 2 hours at about 90% (according to the progress line). Since then, have tried both free and trial versions. On trial, says my license is wrong, still will not let me load free version. HELP!