First out... Nice car My next family car will be a 750.
There are probably those that are going to nag about searching and reading the forum rules, or maybe even the FAQs. But I don't care as long as it's BMW we're talking about
For connecting your HD (HardDrive) to the onboard screen, you probably need a connecting device of sorts.. Easy route would be through a CarPC.
I know very little about the possebilities of the 7-series.
If your just want to hook up a portable storage device for audio. I think the 2008 7-series support USB as mass storage. They defenetly support iPhone/iPod Touch. The Apple way only requires a "iPhone kit" that you can buy from a local BMW dealer, and have them mount it in the car.