Brandon,
JBA's suggestion about a Cable/DSL router is, by far, the best choice. If you already have cable modem access in your home, then I would take the first opportunity to dump those ol' dial-up connections.
The Cable/DSL router costs about $40-60 depending on what brand you get. You plug your cable and your two PC's into the router, and the router manages all of your network connectivity. It assigns "private" IP address to each of your machines (192.168.whatever), and the router itself takes up the IP address. You can have as many connections as the router will support.
The only trick is to put the router in a central location that would allow BOTH PC's to be easily hooked up to it. We can get really creative with wireless points of access, but if you don't need that, it's not worth the hastle.
Let me know if you need help with this -- would be glad to help out. Am a network admin. myself and could probably walk you through the setup.
Pax!
Michael.