In my experience and that of ALOT of PC reviews, magazines, shows, etc... is the NOD-32 Anti-Virus Software. I have it on ALL my machines now. I used a local company here a while back to do some on-site backup and repair for my office machines and they noted that I was using Norton and asked me if I were satisifed with it.
Now, twice, I've been let down by Norton but overall, I have to say that I was not UNhappy with NAV. However, they told me about NOD-32 and I began to research it. WOW!
After alot of reading, I decided to give it a shot and I have never been happier with a product.
I wholey endorse it.
I'm sure there are plenty of places to buy it but I got mine from
www.pcrnr.com (and NO I don't make a dime from the endoresement).
They also have some cool "magic button" software that stores and recalls your pc in the case of a catastophic failure. Do whatever you want to royally screw up your system and then use this to reset everything back to the way it was before the failure. It's incredibly fast and cool... Not the topic at hand, but I thought I'd mention it because I now use that too.
I think NOD-32 may have been that #1 you were trying to remember, Firestorm.
GoPC