The two best anti-virus programs are Kapersky Anti-virus and Panda Internet Security.
AVI is okay for people who are hard for money. But it's not a very good virus program.
Nortons is good, but does use alot of resources and can slow PC's down.
With any virus or internet security program, it is important to download the updates on a regular basis.
I am not a rapt for AVI, if it was all that good, they'd be selling it and making money.