Like Phriend, I don't use Anti Virus Programs. I have a Desktop, which runs almost 24/7. It's protected by my router's hardware firewall. Also i keep Win 2000 up to date. I installed the OS 13 month ago, and do far had no virus problems at all.
Of cause im careful, i dont download executable files from p2p or from sites i don't know.
On my laptop I us a software firewall. Also my wi-fi at home is encrypted.
This worked fine for me so far, but perhaps i reconsider this when the first virus gets in and

up my system.