Sims 3 Generations starting problems?

I installed the Sims 3 generations, everything worked out just fine. I opened the launcher and clicked 'Play the Sims 3' and it said 'No disc found! Please insert the Sims 3 game disc before proceeding'. I've put the game disc in from the start and I've have the latest updates, Base game and such. Please help!!!!!!!!!!!!!!! (ps. It worked just fine before I installed Generations. I used an old game patch for base game before I installed Generations, but it updates automaticly) Thankieeesss