It's steam-only now. If you had the non-steam version, you have to put your original product key into steam and it will register on your steam account, I believe. I added you on steam and I checked your profile, and it looks like you don't have the steam version. Once you have it registered to Steam, you'll have to buy the Ultra upgrade which is $15. Kind of a pain, I know. Basically when Games for Windows Live died off several months ago, they had to change to Steam's matchmaking, which made all non-steam copies useless for online, so all non-steam players were essentially given a free Steam copy.
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