CD/DVD Drive not recognized

Hello,

I suddenly could not play audio CDs, went to My Computer - did not even show the drive. Long story short - got to where yellow triangle shows, tried couple of suggested "fixes", did not work. Was told that Service Pack 3 was corrupted in the Registry. Also checked on Serive Pack 3, seems like it is there, but the other "fixes" had no effect so is Serive Pack 3 coruption in the Registry? Help!