Please go to the CD/DVD FAQ (link below) and follow the instructions to run the Dell diagnostics on your drive. In order to test the drive, you need to put a data disc in the drive. If you are able to insert a data disc and the test passes, then your hardware is fine and we can consider other issues. If you are not able to insert a disc, i.e., the disc is ejected by the drive, then your drive is defective and needs to be replaced.
Please post back and let me know if you need more help.