LAN Multiplayer help

I have 2 computers hooked up to the same modem, both running Windows 7. How can I set up a multiplayer game between the 2 comps? This is important as a convert is on the line
I'm introducing my daughter to BG.

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Start > Run
Type cmd
Press enter
Type ipconfig (in the new black dos box)
Press enter
Write down the number listed next to 'IP-Address:' .
Now start the game, select TCP/IP (should be default) and start a new game. With the other Pc select join and enter the IP-address you wrote down earlier and you're good to go.