I've tried all the other solutions for this but none of them work.

I have my CoD4 disc with its key code and it works fine. I brought some friends over to my room and gave them the disc to install and my key code. We tried starting servers with Dedicated: No and Dedicated: LAN but when they try to connect it says the Key code is in use. We are all connected to the internet through ethernet cables, firewalls are off, PB is updated, etc.

If we use a crossover cable the game works fine, but that only supports 2 people. I thought you could share the key code for LAN parties instead of having to buy 4 copies. Am I wrong that you can share 1 disc (using noCD for the others since I only have 1 disc) for just a LAN game?

Sorry if this is redundant but I could not find a (working) fix to this anywhere.

just find some other keys for the time being, pm me and I'll try and help.

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95% of the people who play call of duty 4 use martyrdom. If you're one of the 5% of people who doesn't need to die to get a kill, put this in your signature.

You don't need to nocd it... the multiplayer aspect runs without the disk in. Try running your LAN without being connected to the net, just run it on a LAN - pull the dsl cable out of the router, or use a switch. Don't know if it will work, but it should be worth a go.

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Like funkymunky80 said, disconnect from the internet and additionally, switch off PunkBuster.
You don't need a disc at all because you can just copy the whole COD folder to your friends' PCs and it will work just fine. Eventually they'll have to enter a CD key (yours or a different one), but that's how it was done at all of our LAN parties.

Thanks for all of your help. Since it is hard to get everyone together I will have to wait to try this out but I connected my 2 computers together using a router and it worked.

I also did not know the game could run with just copy and pasting the folder to a different computer lol.

So would it be possible to connect to the same floor below me (same network, the duplex shares it so we can see each others shared folders) using the normal internet but on a LAN game. I mean we can see each other and all, and it actually WORKED 1 time last year, but never again =(.