From MP3Car.com Wiki
There are many different types of DVD drives available:
[edit] Laptop Form Factor
Laptop DVD drives can be used in CarPC's using a special adapter that allows a a regular IDE cable to connect to these drives
[edit] Slot Load
[edit] Tray Load
[edit] Desktop Form Factor
Desktop DVD drives are 5 1/4" wide with a height of 1 1/2" these are not often used in CarPC's due to their size but some do employ them in their installs.
[edit] Slot Load
[edit] Tray Load
[edit] Multiple Disc Changer
(Photo Here)