The last 2 drives I've had those symptoms with have turned out to be bad.
You could try
1> going to control panel and removing and reinstalling the drive.
2> cleaning the drive with a cleaning kit or a compressed air can.
3> putting it in another computer to see if it works there
But if it has been installed for awhile and has been working fine, i would not have a lot of hope for those options.
Also, have you removed or installed any cd related software between the time it last worked and now?