That's odd. The only issues that I had is getting the game to save as far as GFWL goes. Biggest pile of junk.
The problem is I obviously created a GFWL account when I first installed the game quite a while ago (it FORCES you to do this) I would imagine I had to create a hotmail account as well maybe? I honestly cannot remember I do not have or use a hotmail email account, either way, it's a rancid idea what they have done as for no good reason I cannot play the game unless I log in with the GFWL account I registered the key to. Goodness knows what that was.
This is a problem in ur side. Use the same account of gfw u did registered ur game and u r done. U r trying to play with another account.
I don't know why you are contacting steam support. Nothing they can do since the game requires a GFWL account. Contact Microsoft and next time use the same gamertag for all your Microsoft games. Also, it doesn't have to be a hotmail account. My xbox/GFWL account is tied to a gmail account.
For god's sake. You contact steam support and tell them you're getting a key in use error. They give you a new one, problem solved. It's not steam's fault, it's crackers' faults.
No it's not crackers' fault. It's the OP's fault for not remembering what account he registered the original key with. Call MS and give them the key and say you don't remember what account you registered it with. With any luck, they will at least give you the gamertag/e-mail associated with it and maybe from that you can figure it out.
This Mind you, I have lots of usernames/pws and am clearly partially retarded as I never remember which I use for what. Why do I make life so complicated!? But anyway, OP, do what nhlkoho said; contact Microsoft and see if you can get your gamertag/email via your key. Remember to be polite and explain the situation and they should be good. Anger/rudeness gets you nowhere.
@ OP if you can't get a resolve I can probably give my unused retail disc key if you like, think I still got the game buried in my wardrobe. I will never use the key as I used crack to play the game and I have no intention of installing or playing the game again. Resale value of the game is worthless so it doesn't really phase me to give the key away. But try for a resolve by the methods others have said first .