If you mean that you have the DVD copy, and when it asked for an unnecessary code, you tried to enter it again, that conflicts with Origin, which enters that code to your account just once. There's supposed to be a pause / stop / restart routine to follow when reinstalling from disk to allow you to skip the extra re-registration step. It doesn't always work as intended.
The easiest thing to do is to accept the free digital copy your Origin client will offer you (assuming you are logged into the correct account), download that, and install it.