Internet sharing WIN2K Advanced Server.

I have installed WIN2K advanced server on the same box that has my ISP dial up modem. I have configured the same box as a Primary Domain Controller. My problem is that I am unable to enable internet connection sharing to clients (WIN2K Professional)but all other network functions are fine e.g File and printer sharing, Domain logon’s are fine and the event viewer has not logged a fault. I am also using the 192.168.0.1 local IP range and DHCP on the workstations. As I am new to NT can anyone advise me if I can enable ICS on a PDC or do I require an Internet Proxy server. Any suggestions would be greatly appreciated. Thanks.