I have no idea what to do... I bought the original 1.0 version years ago for $60 and I still have the case and registration code sitting in my desk...

When I try to log on it now tells me that my account is not registered or active, and I cannot for the life of me figure out how to register it. I was under the impression that since I bought the $60 1.0 version already, I wouldn't need to buy the game again... Anyone know what to do? I can't find info on this anywhere.