Elizabeth
The connecton to the pc is only for downloading upgrades in the MPP and transferring Freehand files that are scanned and converted in the pc. The power to the MPP is AC or battery.

In reference to swapping file locations. I keep track of changing locations on the SD card with Fred Melinks program, by putting the card in a reader and saving and printing the index(listed as an option in the menu). However, with the thumb drive for your MPP, or internal memory, be careful about making playlists then changing the location of the source. The MPP will not be able to find it, and you will have to build new playlists. This can be done easily enough, but try to get organised beforehand to prevent too much swapping.
Bernie