Aha, something in my area 
Norton Internet Security and NAV are a good combination. However, NIS is also one of the reasons why you are getting less conversions because of its haphazard adblocking – and frankly I don’t intend to give them a penny.
McAfee has suites as well – in fact, many of the combos are on sale right now – but they have a track record of issuing advisories a little bit too late for some people. Though my cousin was Director of Virus Research there, I wouldn’t give them a penny either.
What I suggest is:
Sophos Anti-virus for your virus protection.
Sygate Personal Firewall for your firewall, but Zone Alarm is also quite good.
For spyware – Adaware is good but don’t let it start up by default, it is a real time and memory hog. Schedule it to run 2-3x a week with your task scheduler instead.