To begin the process, start the Registry Editor.
Click Start, click Run, type regedit, and then click OK.
On Vista machines, Run is accessible through Accessories.
Click the plus sign (+) next to the following folders in the left side of the window pane:
Look for any of the following names in the right side of the window pane:
If any of the items above are listed, right-click on the item and select Delete.
Be sure to restart your computer after you have deleted the files in the registry.
Open My Computer (XP) or Computer (Vista) and check to see if your CD or DVD drives have returned.
In some cases, you may need to reinstall some programs such as CD or DVD burning software, iTunes, or Nero