Service Pack 2

[quiet mike]

SP2 has no AV what so ever. It has a Firewall and a way of checking if you have AV or not. It doesen't override anything. It actually shuts the built in Firewall if it detects the one you have.
Norton Antivirus is kind of old. It's been around for so long, that new viruses start finding ways around it and fool it. I've seen it on my own computer.