if your car is an 08 than NO it cannot play DVD's only the new Idrive 2009+'s can. The nav discs are burned on a layered DVD. I think the laser is the same but yoru idrive system has no codec or program to play the movies.
there are plug in units that allow you to play dvd's in an 08 i drive car. Do a search you should find it.
Also, no, you do not have a built in hard drive. These slots are for an ipod intergration cable (uses both) or you can AUX in just about anything that uses a 3.5mm headphone plug.
I believe you can play music off a USB thumb drive in that slot but don't quote me on that, im about 50% sure.
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