What you could do is set up an old computer like a Pentium1 or similar as a Software router/firewall. It is obviously becoming quite popular as many people have broadband. A Linux OS or a dedicated router/firewall distribution will do the trick. A Linux router can run Samba (a networking server) to share files across the network.
Generally, the dedicated router/firewall distros (
www.smoothwall.org ,
www.ipcop.org , and
www.freesco.org ) don't support being a general-purpose file-server, as that goes against the "keep it as simple, and therefore hopefully secure" philosophy of security devices, which is what a firewall is (but it sounds like you've got a hardware router anyway.) So slap a default build of
NetBSD (or Linux if you insist
) onto your "spare" box and you'll turn a PC that won't even
think of running XP into a super little file-server. Let us know if you need anymore help with this
