I had purchase TWAU through amazon and I got the activation key for it and then I hit download I keep getting this error message on my computer saying " This installation package could not be opened. Contact the application vendor to verify that this is a valid Windows installer package." I was told to ask you guys for a Steam key. Does that mean I have to play the game through steam. I don't have an account with steam. And if so how will I use the key on steam where would I go to prove that I had purchase the game? I need help cause I want to play this game but I don't want to pay for it twice.