This key will work for any GFWL game.
I'll sell it for 10 dollars via paypal,
To use:
1.you will have to find a installation for one of these games. Be this warez or a disc, both will work the same.
2.when you click "live" ingame you can sign in with your gamertag or make a new one, then you enter the key.
3.enter the key and presto achievements and moultiplayer!