If you are using two modems then you do not need to use automatic IP addresses. Assign each NIC a static IP on the same subnet. Use a private address so not to cunfuse any thing. Try a set up like the following :
Computer one Computer two
IP address 192.168.1.100 192.168.1.101
subnet mask 255.255.255.0 255.255.255.0
Leave everything ekse blank since you will not be using the NIC's to access the internet only the other computer. Go to the computer name tab in the properties of my computer and verify both computers have the same workgroup name. Share a folder on one of the computers and then go to the workgroup in My Network Places to make sure the other computer and the folders show up properly.
edit: I suggest using a different IP range, and a private range, than your modem so none of the internet connections can access the other computer easily.
Edited by Baltboy, 16 January 2011 - 11:57 AM.
Get your facts first, then you can distort them as you please.