Security on a ghetto Windows machine

I've got an old Compaq Proliant 1600 here I need to run Win Server 2003 on for school stuff, but much to my dismay it picked up about ten virii and three worms in the ten minutes it took me to grab some drivers and hit Win Update.

So, my question is this: What's the best antivirus proggie and firewall to use on a machine like this, which doesn't have much power to waste?

It's only got 192 megs of the RAMs and two Pentium2 450 processinators, Symantec Corp. and Sygate Personal Firewall are really slowing me down to a crawl. Plzhlpomg!!1

If you can hide behind a router that'll help you get the stuff you need before you pick up viruses. If that's not feasible download the stuff onto a CD from a computer that's known to be safe.

As for the stuff, Anonymous recommends:
Zonealarm (although it seems to get more bloated with each version increment)
Everything from http://www.grc.com/

That's about it. I wouldn't bother with a virus scanner, so long as you're not a dumbass who downloads viruses manually nothing is gonna get in through your firewall.