If it's got a 386 processor and 32MB of RAM, and you can find a pair of Ethernet cards, you can turn that Junk PC into a serious Firewall to protect your network.
We walk you thru the installation on this episode of Systm: It'll keep your network seriously safe.
It's essentially a stripped down and focused Linux distribution that does nothing but stateful packet inspection, Snort intrusion prevention, IPSec VPN, and plug holes bad gals on the Internet might use to get on your network).
The main trick in setting up IPCop, after, of course, you've found an old Intel/AMD/Cyrix/Via/whichever machine that still runs, is securing a couple of compatible Ethernet cards... check cards against the IPCop Hardware Compatibility List before you buy 'em!
You can download it here... we prefer the ISO version you can burn to a bootable CD-ROM, it's called "ipcop-1.4.18-install-cd.i386.iso"
Check out the documentation before you start, and definately take soem time to check out the laundry list of IPCop Add Ons you can use to customize your IPCop installation with various filters, servers and (sweet!) OpenVPN.
Check it out!