www.pricewatch.com
Well since your CD-Rom was working, correct?
Have you recently installed any new hardware?
Have you recently taken out any hardware?
Have you checked your power supply to see if it getting enough juice?
Have you checked the drive updates(older cdroms)?
If any of these aren't the fix, then you may have bumped it when it was opened and knocked the belt on the gears loose. There is no way for you to fix it, unless you know what you are doing, if it is a nice cd-rom, take it to a Computer place and have it fixed.
Another thing is it may be dirty. Sometimes the laser that reads the cd gets residue on it and has trouble reading cds so it just says there is nothing there. You can go to walmart and spend a few bucks and get a cd-rom cleaner kit and pop it into your drive and that may do the trick, this happens to cd players too.