NAT On W2K Server

I am not able to connect to the internet from Client PC’s, Direct dial starts but no connectivity to the clients, the Server can connect fine… when I try to configure NAT it asks how the other computers connect to the internet, I choose the Network card, and the NAT wizard tells me to install a network card, but one is already installed…. BAsically I am asking for a point form instruction on how to configure and setup NAT…. any help or advice is greatly appreciated….