Llama gave you some good advice.......although I prefer my ESET Smart Security 4 over Norton..although reports say this Newest Norton2009 Llama recommends has alot less bloat than the other past versions....
The main reason I recommended NAV2009 in this case was Symantec's tech support. They WILL spend an inordinate amount of time on the phone with you to get NAV installed and scanning and cleaning. The NAV install disc is also a self-booting virus-scanning disc, and is invaluable when dealing in an already-infected system.
If a system is already pretty clean and you just want to protect new nasties from coming in, or if you already know what you're doing when it comes to cleaning out an owned system, then I recommend Eset's NOD32. Their tech support isn't as good, IMHO.
If you're looking for a full suite, both ESET Smart Security and Norton Internet Security 2009 are the ones. Eset SS is leaner and meaner, while NIS gives you a lot more security tools while still managing to stay out of your face. As it happens, NIS is cheaper. As I've posted earlier, both have essentially the same gaming benchmarks on modern systems.
Both have good detection rates, and both have great "smarts." That is, they automatically go into "game mode" when full-screen programs are running (so they won't run full scans or get updates while a game is playing), they both take the appropriate action to viruses automatically without asking you a lot of stupid questions (do you really want to save a detected virus? only if you're a researcher like me), and both have firewalls that automatically know about thousands of "Good" software that it shouldn't interfere with. In other words, AH just works without the firewall prompting you to ask if it should let AH connect to the Internet. All of the free products will interrupt you to ask you idiotic questions like this.
-Llama