When I open the formatting function I get a choice of which drive to format. There is a long number which is the system drive, plus whatever other drives I have active. If it is a zip drive it should say so, though CF drives may not be so obvious,
If you are unsure, just remove all media so the only drive left on the list is the system (C) drive. It;s imperative that you do not select this. Then when you insert your media it should then be obvious which one it is so you can avoid it.
The latest version of mpc editor seems to have the format function disabled, so you need the previous version.
Hopefully your system will look similar or else look more obvious.
If you have any problems, get back to me .
When you format using mpc editor, the disk has just one partition (something you cannot do on the mpc3000). This allows the computer to access it as well as the mpc.
My mpc3000 cannot see a zip or cF card unless it is mpc3000 (or mpc60) formatted. (are they all like this?). So I need to format on mpc editor before I can use a disk in the sampler.
Hopefully Mike at Midicase will not abandon his creation for ever. Us 3k users need it.

On my computer, the number beginning with ST is the system drive. But the others are fairly obvious.
Yours may look a little different