I use a hardware firewall. IMO, it is a lot beter than most software firewalls.
and I have Antivir Personal Edition (v7 Beta)
it is light on resources, and works really well. it's also free.
one of my friends used to use Avast, but it expired a couple of months ago.
and just a couple of days ago, I recommended Antivir. he downloaded it, and once he installed it, the amount of virus detections he got was crazy.
a full scan deleted over 1500 viruses on his computer.
and just having it on guard mode before that deleted over 100
anyway, he learned his lesson the hard way.....