The story changes:

Maybe not a hard disk after all but a "means of mass storage" - this does not have to be a hard disk I suppose?
see http://www.synthzone.com/ubbs/Forum37/HTML/002857.html
for other possibilities?

usb memory dumps to pc and back? yes please!
lots of custom memory? yes please!
flash cards? yes please!

ps. I hope its NOT a cd writer, but some of the other ideas would do nicely thanks.