Two network card on W2K and one router

I have 2 NIC, one is Accton EN1207D-TX PCI Fast Ethernet Adapter, the other one is 3Com EtherLink XL 10/100 PCI NIC (3C905-TX. I have 1 unit Cisco 770 series router connected to ISDN 128 kbps. I have installed Win2K advance server. One of the nic connected to the router and one of it connected to my LAN. This router, is indicated to dial-up to the internet. Now for my problem, I cant make internet sharing with this 2 NIC and the router. The NIC cant talk to each others. How can I resolved my problem. Please help me on this. Thanks.