Personal Firewall Software

greetings!
I have a quick question that's quickly going to escalate into a complicated one. I have a laptop that I'm soong going to be taking in to school for use during class, and there is every chance that I'm also going to be connecting to the school network. (that is, I'm in the IT department and connecting to THEIR network.) I don't feel particularly comfortable about doing this without a personal firewall, but I'm not sure what to use because in all honesty I've never needed one before. what do you suggest I use, when my computer has the following specs:
AMD K6(2) 475Mhz
192MB RAM
Windows XP with SP2
Symantec Antivirus Corporate v10.0.0.2.2000

also, price of the program is irrelevant, so feel free to suggest expensive ones as well as free ones.
thanks for your help.

p.s. if you suggest I use Windows Firewall, I will carve into your head with a spoon and eat your brains with it, because you don't deserve to have those brains. not that there'd be much there....

... something I forgot to add in >>22
If your school has done even a moderately decent job with their network, they won't allow two wireless clients to talk to each other. Sure, it's theoretically possible to masquerade as an AP and send malicious packets, but that's in the realm of incredibly unlikely. What I mean is, 99.9% of the people there will not have the ability to pull it off, and the other 0.1% won't have the interest. What good is owning a shitty Windows laptop in school, anyways?

Encryption is probably gonna be the most important thing for you, although with Windows, I suppose a decent firewall is pretty useful anyways :shrug: