CD and CD/R not recognized by computer

My computer, a Dell Dimension 4600, is not recognizing either of the CD devices.  I checked device managers and located the CD/ROM, but when I clicked on wizard to find new hardware, the device was removed from the list.  I rebooted the computer and the E drive came back.  I burned a CD on it, then it was no longer recognized by the computer.  I have never had aproblem with the factory installed devices. Since the one reboot that I got the burner back, I have not been able to get the devices running.