Wow, I haven't checked this thread in a while. It looks like the hard drive is designed for automotive environments, but that's not to say a normal laptop hard wouldn't be fine. With a rotation speed of 4200 rpm, I would think a 7200 rpm wold help speed up POI searches. However, finding a 7200rpm PATA hard drive might be difficult.
As for the OS, if it is QNX, then it could hold lots of possibilities. From what I have read on the OS, it's about as feature rich as you can get for an embedded operating system. However, not much can be done without the source code. If someone were able to get the source code from bmw, the possibilities would be endless.
Here's a screen shot of the QNX gui:
