Call of duty 4 singleplayer problems. pls help!?

When i try start my cod4 single player, it just clonks in the dvd-drive and does nothing. Mutiplayer works just fine. And i cannot uninstall it, because id does not show in the page that shows my installed games and stuff. And nothing works in the game menu that shows up when i put the disk in, it just closes itself. This all happened when we put some new parts to our computer. Before that it worked just fine!