Linux system as firewall on windows ISA systems.Any suggestions?

Hallo to everybody This is my 1st post in this forum so be extra patient everyone
Now the thing is that I have taken an assigment to setup a linux system as a firewall to about 20 pc's with windows!Sounds fun but i know very little about Linux I am using the RTFM tactics but has little or no effect
Thing is I have to w8 for the rest of my class to set up the rest 20 pc's
Sth last is that we are working with crapy PII that our univercity has + I"m windows generation and i certainly need GUI
I was thinking Madrake for it has the best compatibility with old eq.
If anyone has any fresh ideas or any tickling details that will be helpfull be my guest koz I'm on a deadline
Thx in advance

 

http://smoothwall.org/

 

IP Cop is also a great firewall.

www.ipcop.org check it out. no need to know linux commands, you can access your ip cop machine from a web browser on any windows computer. you can set everything up from a GUI

 

1st of all thank u all 4 supporting me
2nd) every other student in my class chosed setting up the isa different sections each, and I've chosen to set a Linux system as a firewall so... it has to be Linux
I mean.. is it difficult when everyone's finished setting up the isa systems to put mine as a firewall above them???
Is mandrake a right desition?
Forgive my poor english btw