The computer will act as a firewall/router. The problem is you need to have a unique IP address on each machine, and your cable modem only gives you one. So you do it like this:
Cable Modem-----------216.24.23.244 XP MACHINE 10.1.1.1-----HUB------Win 98 Machine 10.1.1.2The 10.1.1.1 and 10.1.1.2 addresses get masqueraded and appear to the outside world as both coming from 216.24.33.244 (or whatever IP address you get from the cable company).