The game is permanently linked to the original account it was registered to. You can install it again, under your own account only (the original); only one instance can be running at the same time.
Only one instance of registration is valid, so you have to pause the disk install where it wants to have you re-register, then when you "Continue", it should skip over the extra registration attempt.
https://answers.yahoo.com/question/index?qid=20120704172409AAW6jdE