Check Cable Connections

• Your computer may not see the drive at all or have only the barest connection to it if the cables connecting it to the motherboard are loose or faulty. Verify that the cables are all securely fastened and reboot your computer. Check the length of the cables for signs of fraying or defect, as the cables themselves may be faulty and causing a problematic connection.
  
  

Driver Problem

• Hardware drivers can become corrupted or out-of-date without warning, which can cause problems. Check for driver updates for your optical drive and all other hardware installed on your computer to correct any conflicts that may be occurring. Your operating system may require an update as well, so try finding the most recent versions and updates for all components within your computer.
  
  

Media Problem

• Your computer may have trouble reading your optical drive because of the disc inserted. A CD drive cannot read DVDs, or the disc itself may be dirty or have fingerprints that are preventing proper reading. Verify that the disc you are attempting to read is playable in your drive, and that it is clean and free of scratches or cracks.
  
  

Faulty Drive

• Not every single item works perfectly when it comes off the assembly line, and it's possible the drive in your computer is simply defective. Try swapping your drive to a friend's computer to see if it will work, or put your friend's drive in your computer. If your drive still refuses to work, or your friend's drive works fine in your computer, your optical drive may be defective and require replacement.
  
  

Uninstall and Reinstall

• In some cases, the optical drive's drivers have become corrupted or otherwise compromised, causing the problem. Enter your computer's Device Manager and search for DVD/CD-ROM drives. Uninstall the driver listed and reboot. When the computer boots up again, it will detect the optical drive and automatically reinstall the proper drivers.