Sharing Internet Through NAT

Hi,
I have two NIC card on my windows 2000 adv. server and i am using dialup connection.I want my 25 clients can share internet but i don’t want to use ICS and any proxy server.I want to do it through NAT.my first NIC ip is 192.168.0.1 and second NIC ip is 192.168.100.1 i make my first NIC as private network and second one is public network.I enabled demand dialing also but my clients cannot share internet.How i do it.
Is there any web site which gives me connectivity for this.
Anurag.