Hmmm...it should work. have you got it registered with Steam? Download Steam client, create and account and then register your CD key with it. Remember, your CD key will be permanently binded with that particular account. After that, when you start Steam with your account, it will show the games that you can play under "My Games" or something like that category. Now its a simple matter of upgrading the game to 1.6 and then playing.