I've also had this problem. I bought the Sims 3 at game stop a while ago and I've played it on my pc a good amount. Though I stopped playing it for a while. Then recently I felt the urge to play the game, but my origin account said I had to reinstall it. So I did then it said my code ha already been used. I have the box and everything. I can't even use my expansion packs any more either because I do not have my sims 3 installed. WHat should I do?
Where are you reinstalling from ? Origin download or the DVD ? You don't need to register again just install from the account you have the game on.
