Norton is by far not the worst AV I've ever run. It has, in the past, had a tendency to get big and bloated, and severely bog down a PC when scanning. I hear the latest versions have slimmed down quite a bit. McAffee, in my past experience, is about one step better than not having an AV program at all. Kaspersky, well, I've cleaned viruses off of systems that had up to date definitions in Kaspersky. I'll never recommend that program. Personally, I've found the free-ware to be just as good as any of the top players: AVG, ZoneAlarm, or Microsoft's Security Essentials (currently running this one). I've got MSSE set to full-scan my system every night around 11pm, after checking for and installing updates first. Since Google started flagging ww2aircraft as infected, I've turned off the "block suspected sites", and MSSE has come up each morning with a clean bill of health. Hopefully the ad that was causing the issues has been identified by Google/whomever, and nuked...but it hasn't caused any issues on my system. And, for the most part, viruses have to be invited in. They don't just install themselves. You have to click on something, be it an infected site, email, or file. If you're not sure, don't click.