Sims 3 Registration Code help?

Hello. I would like to register my game on the Sims 3 community site and as I do this it says I need a 'Serial Code'?? I do not know whether this is the registration code used for the game installation but that would be of no help anyway as I do not have the manual where I believe it is located. Could somebody help me by telling me where I could find the serial code on my computer? I found a very useful answer for this just recently but that must have been for an XP computer and it said 'RUN' which the Vista doesn't have. Also I think the layout must have been different as when I go into the sections it is talking about I cannot find the tabs. Please help :(