Hi, chances are that you need to do the following: go to control panel/network and select properties of your TCP/IP->ethernet adapter. If you don't have TCP/IP bound to your ethernet adapter(s) then add it in this same window by clicking: add/protocol/microsoft/tcp/ip
Now, after selecting TCP/IP properties of your ethernet adapter,
then select the IP address tab and enter 255.255.255.0 in the subnet mask field of ALL the computers on your LAN. Then specify a unique IP for each machine, such as 198.168.50.1 for one machine and increment the last digit upwards for each different machine.
You may also want to open your IE browser and under tools/internet options/connections, select "never dial a connection" so that your machines do not try to access the internet when you start up a LAN game. You can add a manual shortcut to your desktop by copying your connection from the dial-up networking folder to your desktop. Clicking on this will do the dialing for you before you open your browser for surfing!