no disrespect but firewalls and antivirus are pretty much useless these days.
Your router / nat / dss connecction will give you (ok - should give you) adequate protection from internet borne worms and other nastyness.
Your best defence these days is good anty-spyware stuff. Modern virus mutate too frequently for AV to be worth much, unless you are worried about, well,s tuff that propagates over a internet link - that is firewalled at your router.
I'll try to write a longer post when i'm less drunk, but basically if you want to be 100% safe use windows policies to whitelist all executable files, with their authentity checked via
2 hashes (md5 & a.n.other) - just one is burte-force breakable. trust me. Nothing else is effective any more. You can buy viruses over the internet, almost on an open market, that can easily evade or subvert any firewall / AV package you care to name.
Depressing, but true.
The best defence is, as gotta put it:
I have not once been hit by a virus, and only hit by spyware once when I just was being an idiot and not paying attention.
Firewalls and similar software makes you lazy.
good luck.