[reboot]

Opinion time.
If you're running a firewall (Sygate or ZoneAlarm, I don't care for Black Ice), and you're using common sense (I know, oxymoron), don't download junk from crap overseas unknown sites (use C|Net or Tucows, a few others), you don't NEED any anti-virus program.
You can't get a virus from email if you use a text email client (In other words, get rid of Outlook!!!!!!), turn off MS scripting (that's the VBS stuff everyone is WAY too paranoid about) if you don't know what you're being sent, don't click on it!!!!!!!!!!!!!!!!!
Email trojans are infectious because when you get an attachment it's like a kid in a candy store, who just got his allowance. Resist the urge to see that "nakedteen.jpg" file you got sent, and you probably will never get a trojan.
As for having an anti-virus scanning web pages, it's a total waste of resources. A firewall should prevent any malicious attack embedded in java or HTML, so why are you running both?
I keep an anti-virus on my machine (InoculateIt), but ONLY open it, and scan downloads that may be suspicious. I don't use Outlook, just a text based email reader (Eudora Light 3.01) (You could use the new Eudora 5.2, but disable the "Use Microsoft Viewer" portion).
I don't believe in the "trade off" position. If I can't control my software (and hardware) I get rid of it, and get something I can control.
Norton (yes, anything by Norton), McAfee, Panda, PCcillin, and most others (that are NOT free, BTW) are junk. PCCillin being the best of the worst.
The absolute best protection is a Router. Once configured correctly, you don't need any other firewall.
The next best protection is removing your finger from the mouse button before you click on it.