Or http://www.freesco.org for a free firewall and I'll bet you can find someone with a 386 that will give it to you for nothing.
I've used freesco on a discarded "doorstop" box for a cheap print server when the company wouldn't authorize a JetDirect. Works well if you don't mind the space it takes up. Just turn off the monitor and remove any hard disks to cut power consumption. (Freesco runs from a floppy.)
