ok.... i downloaded avast4 home a few weeks ago, installed it, did a startup scan, and deleted all virii, trojans and worms.... had system problems afterwards, so i backed up, did a full re-install and re-downloaded avast4.
it worked fine, until i registered, at which point it told me the registration code was old, and refused to download updates..... i'm using XP pro sp1 on a P4 2.6ghz with 512 mb ram and 80 gb HD.... little help?