Multiple partitions on the internal harddisk?

So I just bought the WD TV Live disk, and I plan to connect it to a NAS disk I have. The NAS doesn’t support sharing folders but only partitions, so I was wondering if it’s possible to divide the internal WD TV Live disk into several partitions, one for each type of media, and still have them be recognizable and have the menu appear once it’s connected to the TV.

No, you cannot repartition the internal disk, nor is there any reason to do so.