configuration problem in nat

i have configured win2k domain controller in a dual processer intel server. here i installed two nic’s, 1.intel, 2. 3com. one is allocated to private ip address, and other one is allocated to public ip address. My domain controller is connected through radio link modem to an isp. My bandwidth is 512 kbps. the network is already configured with unix server and the networking is working.
here i am configuring a new win2k server as a domain controller in unix network environment and converting all the clients to the win2k network.

Our usage is mainly for browsing the internet