[citation][nom]elcentral[/nom]i had 2 friends ho owned Norton 2 ears ago and they had pc problems, installed avg and it found 5 viruses in Norton and around the pc fixed all the problems at no cost.[/citation]
I've seen countless problems with Norton, McAfee, AVG, Kaspersky, Avira, ClamWin, BitDefender, TrendMicro... the list goes on. No AV on the planet finds everything out there. When we have an infected system, we generally do 8-10 different virus scans on it, nearly all of them finding stuff.
The worst problems a few years ago were from Norton. Today, it's Kaspersky and McAfee. Norton was re-written maybe 2 years ago and has shown positive improvements. Detection rates are always around 50% for these antivirus programs, so it comes down to how often it messes up windows that makes a particular AV a bad or good choice. I still see many systems with AVG problems today. Mostly it's "it wants to reboot my computer every single day".