Hi occam,
I would suggest you to check if the DVD drives are detected in the BIOS by following the steps mentioned below.
- Turn on or restart the computer.
- Immediately at the Dell logo screen, starting tapping the <F2> key once a second until the BIOS screen pops up.
- Using the Up/Down arrow key move to ‘Drives’.
- Expand the ‘Drives’ by press +/- key.
- Check if the DVD drives are detected.
- Let me know the results.