Dvd missing or currupted - Dell OptiPlex™ GX270 PC Desktop

Click on Start, Run, and type regedit and press Enter
Click on the plus signs (+) next to the following folders

HKEY_LOCAL_MACHINE

SYSTEM

CurrentControlSet

Control

Class

{4D36E965-E325-11CE-BFC1-08002BE10318}

This folder is the DVD/CD-ROM Drive Class Description in the registry. Look for any of the following names in the right hand column.

Upper Filters

Lower Filters

Upper Filters.bak

Lower Filters.bak

If any of the above keys shown in step 4 are listed, right-click on them and choose Delete

After deleting the keys, close the registry editor
Reboot your computer
Open My Computer and check to see if your CD or DVD drives have returned. You may also want to open Device Manager and verify that the yellow exclamation and error code on the CD or DVD drive is gone.

hope this helps