COD 5 Lan problems

Hey if someone can help me that would be great.
I got COD 5 for my birthday and i love it. I have 3 computers in my house and all other games we all play on a lan. We try doing a lan on COD 5 but it keeps kicking one of us off for the same cd key. Does anyone know how to get COD 5 to work on lan, particularly zombies) with only 1 cd key. We have tryied using some of the cracks but we dont know how to get them to work. Any help would be great.

We figured it out. A big pain this is the first cod that has all these protection thing in it.

Well the game is really dumb on how their lan works. Like all the Call of Duty's you can play multiplayer without the cd and as long as your not using punkbuster you can play online with friends sharing your cd.

But Coop is another story. We figured out that we both had to be offline in order for it to not kick us from the main menu as it did when one was online and another logged in. So we disconected the internet(we have wireless) and using a ethernet cord conected our pc's together. Then we downloaded a COD5 lan hotfix that you activate after you get to the main menu by minimizing the game. Then we were able to play with each other on the lan playing Zombie's