AVG free edition for AV and Zone Alarm free firewall. I used to pay for AV and firewall softwares until I tried those 2. They work well together and protect your computer as good as the nonfree ones.
I have installed NAV, NSW and Norton Internet Security 2005. I am not happy with any of them because of the time and memory consuming, so then what?......aither free or pay for.
Give me three choices as per your experience, past and present......one million of us will than you!!!!

Chowhound
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GameFAQs
GameSpot
Giant Bomb
TechRepublic