>NAV is probably the worst to entwine itself into the OS. I've used McAfee for years and never had a problem.

Just to provide some balance to this discussion, I've used NAV for years and have never had a problem. For that matter, McAfee failed to detect the only virus I've ever personally encountered (a Word doc infected with the W97M.Ethan.A virus) whereas NAV detected it. I have to say though that McAfee's web site was the more helpful of the two in providing details and instructions on how to get rid of the virus once I'd found it.