I use McAfee coz it updates it's self...and Outlook Firewall coz it's simple yet very powerfull and free

As for Spybot and Adaware....I think Spybot is bordering on being an AV since it removed Dialers and Hijacks which often behave in similar manner as Viruses, though technicaly not viruses but still.....also...Ad-aware can't hold a candle to Spybot. :P

- Noia