Entered the code but not showing up in my games menu

• Are you logging in with the same account that you originally used? 

Look at these two links if you are:

• http://help.ea.com/en/article/origin-my-games-list-is-blank/
• http://answers.ea.com/t5/The-Sims-3/FAQ-Invalid-and-Used-Serial-Codes-amp-Games-not-showing-up-in/m-p/194028

Im on the same account and it is on a cd but i have reset my computer so could that have wiped it? 

If you registered it - nope. Contact a game advisor: http://eahelp.ea.com/en/ . For help with navigating the site, see this: http://answers.ea.com/t5/Beta-Archive/How-to-contact-a-Game-Advisor-using-the-new-EA-Help-page/m-p/2161281