If when you attempt to register it, you get a message indicating that the email does not match out records, it means that the serial you have has already been registered--that is, you've got a used copy. Once a serial has been registered, it cannot be removed from that account and registered to someone else.

You may have some options, depending on where you bought the game. If you got it from eBay or some other place where you can contact the original owner, you can ask them to turn over their account in its entirety and change the name/email on it to yours. If you got it in a store and it was marketed as a new copy, you can should be able to return it for one that really is new, not a rewrapped return.

If it was marked as used and sold to you by a third party though, your only real option if you want the updates is to purchase a new serial (at reduced cost versus the whole game). If you're interested in that avenue, contact [email protected].