log into the router
http://192.168.1.1
put in your password
click the advance tab
then click DMZ
you will need to get the internal ip address of the computer that will host the game. i.e 192.168.1.1
to find this out in win2k/xp go to start> run> type cmd> then at the dos prompt type ipconfig
next you will have to forward the ports (by click the forward tab in the advance settings) to the computer that is running the server. different games run on different ports. so that is something you will need to research out.