i haven't have any problems. you have to give them your email of somekind so that they can send you the key, so that you can use it forever. make sure when you register, you uncheck all button that asks you if want to receive email in the future. but you have to check automatic update. i think the major problem with avast and most anti-vrius that also scans trojan horses and worms have a problem. that is, it finds that the system restore file as a trojan horse. so, that may be quite annoyin gbecause win xp home, tends to save a restore almost everytime there is avast update. and every time this happens, avast sees it as a threat, that you may want to ignore. but, i haven't have that problem, since avast downloaded a patch (automatically after a few days). i can still system restore my win xp. i mean, avast home 4.6 is not as great as some professional versions, but for something that is free, i found it worth a use. The best thing about avast is, the automatic update is served by 7 servers in the 6 continents, so whenever there a new virus, the local servers locates them immediately allowing avast to prevent it from spread into your computer. no other providers do this, which i think is pretty unique.