do you mean the cd draw wont open?
look in "my computer "does the cd player show in this if not the power cable must have come detached from it inside, or you could try switching the pc off and back on again,
sometimes works
there is usually a little button which you press very gently - on my PC it's in the top right hand corner of the recessed top half of the stack. You probably know that anyway so why not try switching off for about five mins then rebooting. I remember a while back |I had lots of problems with things not working and it was cos the air vents were blocked. I don't know much about computers but expect the experts will soon sort it out for you.