Hello,  There are two list servers that I receive related to
Disklavier.  One is a Yahoo group and the other is run by Yamaha.
About 10% of the submissions seem to be about finding formatting and
using the old 720K floppies -- rather boring reading, and unfortunately
the Yamaha-sponsored group has no archive; I think the Yahoo group
might:  http://Yahoogroups.com/group/disklavier 

Yamaha's Disklavier User's Group (DUG) home page is
http://www.yamaha.com/yamahavgn/CDA/ContentDetail/Text_WithCatMenu_SC/0,,CTID%253D202700%2526CNTYP%253DGENERAL,00.html 

I do not own a Disklavier but I receive the list mail.  Here is a
summary of what I remember about floppies and the DKV:

The best way to play the DKV is with a computer and the MIDI-In port.
I don't know if there is a suitable MIDI-OUT port for recording from
the piano.

A 1.44 Mb floppy diskette can be faked to a 720K by covering the hole
in the cover (the one that is not the moveable write protect hole).
You can then format it on the DKV or on another computer.

There are ways to format 720 kb diskettes on various operating systems
but I don't remember the details.  The Yahoo group archives might have
the answers.

There still are sources for 720 kb diskettes; they even show up on eBay.
Prices vary.  I remember reading the letter of a DKV owner who was very
proud to have bought a huge quantity of them at almost $1 each.  Doesn't
sound like a bargain to me.

Yamaha sells upgrades with CD but I don't think there is one for the
MK-100 model.

Best regards,
Spencer Chase

 [ A good overview and many links are at
 [ http://www.pianoguru.com/midi_&_disklavier.htm 
 [ -- Robbie