I want to share files with my room mate but not allow internet access, He has his own source for internet. He connects to his modem via cat 5 and to mine via wireless. He has 2 separate NIC cards to accomplish this. So far I haven't been able to get it to work. Any advice?

Hi,
Im at a loss as to what is the problem. You say he connects toyou via wireless?

Sorry didn't explain that very well
What we are trying to do is have him connected to both his network (internet) and my network (file sharing but no internet) at the same time.

Hi,
Since you say that the other computer contains two NICs, use Control Panel >Network to set the wireless connection(NIC) to a static address(make one up.) Generally something like 192.168.0.1(which is a default router address or 169.254.0.1(which is a APIPA address) and give the other computer a similar address(not the same.) The default mask should work; it should assign it automatically. This is done with the IP Address tab and the Gateway tab. Set the gateway on your computer to be the computer with the two NICs by giving it the IP address assigned to the other. Do not have DNS or WINS turned on on that card. Do not tamper with the settings on the other card.
Hope that was clear and helps,
crigby

When you connect to two networks like this, you are also getting two gateway addresses. Your computer will get confused as to which one it is suppose to use for routing. You will need to set the Binding Order on your network devices. Set your LAN connection first and your Wireless connection after that.

Vista - Start, Network, Network and Sharing, Manage network connections, Press the ALT key to see the Classic Menu, select Advanced, Advanced Settings.

XP - right click on My Network, select Properties, Advanced, Advanced Settings (hope I remember that right).