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....

>>3 I didn't ask for OS advice. I like windows. sure, it fucks up, but it fucks up in a reliable way that I know how to fix. I asked for personal firewall advice. so, in closing, stfu, get out of your mum's basement, have a shower, and stop being an opensource shill. you get what you pay for, after all.