Windows Media Center will ONLY BE DISTRIBUTED W/NEW PC's.
I have to be carefull what I say here, since I work for Microsoft and I am on the internal beta for Media Center.
For what it is intended, it rocks. Here is what you get.
Music Navigation and Playback.
Photo Navigation and Slideshow Playback.
TV Tuner w/PVR functionanility.
and more to come in the future I am sure.
You can hook it to your TV and use a remote with a USB IR reciever to navigate the system.
I works really well, however, I don't think that Microsoft is intending for people to put it into their cars.
The interface looks awesome, however, I love the Aqua XP look, so I am biased.
I have all my WMA files on it and I love it.
Feel free to ask me questions. I cannot garantee that I can answer them, due to NDA but I will try.