what's this "Onboard DC-DC Power Supply" for the N330?
You can get both the N230 and N330 version with or without Onboard DC/DC Power Supply.
The versions with onboard DC/DC power supply comes with an external 19V, 90W AC/DC adaptor just like the adaptors used for laptops.
For Car-PC use it would be much easier if it required 12V instead of 19V. Instead you need a 12V to 19V external DC/DC adaptor to run this from 12V in a car.
The versions without onboard DC/DC power supply requires an external ATX power supply instead.
You can get an intelligent 12V ATX power supply from the MP3car shop to run this in your car: http://store.mp3car.com/category_s/22.htm
This is probably be the best solution for Car-PC use and the version without onbaord DC/DC converter is also be a bit cheaper although not much.