Computer won't play game discs

When I insert a game disc onto my computer such as The Sims or Sim City 4, I can get as far as the game menu but when I hit play it just closes and nothing happens. Both of these games used to work fine until now.

DVDs and CDs both seem to be working fine. I've tried using an external disc drive and the same thing happened. I'm getting really frustrated; cab anyone help?