the way it works is the origin account and the sims 3 account use the same email and password which then ties your code to that account but since you made an other account your getting the code is used message so you need to contact CS so they can assist with mergeing your accounts
to contact CS here's how
http://eahelp.ea.com/en/contact-us/new/
or
1. https://help.ea.com/contact-us
2.Set your language to US at the bottom
3.Describe your issue with a few words
4.Select Product: The Sims 3
5.Select Category: Billing/Purchasing or Account Management
6.Select Platform: PC
7.Click Find solution
8.Scroll down and click I still need help
9.Click Chat Now to chat with a Game Advisor
Hello, I have simular problem, I bought The Sims 3 DVD, there was 2 DVD I instal that , and on beginig Thay asked for serial code, I write it and than instalation go on and finish as I say. But when I go on Sims to play game they asked me for registration code, I found code in Registry Editor but it didn't work. So what to do?
