I'm not really doing this anymore, but i'm still intrested in knowing how. Lets say for example that I have a MUD (for those who don't know, it's a small text game) running on my linux box. I would use the windows box (because it's dialup and i'm cheap and can't buy a better modem) to get onto the internet. If someone were to try to connect they'd be trying to access port X on this machine, and not on the linux one. If it had it's own the windows box should route all traffic addressed to the linux box to the linux box.
Or maybe I want to connect to a MUD but it only allows 1 player per ip address, and I have a friend over who also wants to play. It'd be no problem.
just curious, i'm sure it's possible. just dont know how.