Ide cables are unreliable over a couple feet.
You need to use a usb enclosure for your disc drive (if you plan to mount it in dash).
If you mount laptop in the trunk, you'll probably need a powered usb hub up front to run the drive also. MOst long usb runs (12-15 feet) cause power issues when running high draw devices like a dvd/cd drive. Hense, the need for a "supplimental" power source........
Cheers
(Edit- hmmm, need to type faster it seems

)