My name is Varun and I work for the Social Media and Community Team at Dell
Verify that the optical drive is enabled in the BIOS (press the power button and start hitting F2 key to enter to bios)
If Drive still not detected, Load BIOS defaults.
Link for Microsoft fixit for optical drive http://support.microsoft.com/kb/982116/en-us
and even after that if you don’t find the optical drive in my computers then the dvd drive needs to be replaced .
Let me know if this helps or if you need any further support please reply us back