Click start, type in: Device Manager
Click on Device Manager, and check under DVD/CD-ROM Drives to see if the DVD Drive is listed. If it is, then uninstall it from Device manager and restart your computer.
If you don't see a DVD Drive listed, then it may be a cable problem, turn off your computer. Open the case, and make sure that the cable running from the back of the DVD Drive to the Motherboard is securely attached.
Good luck,