I've had success formatting 1.44MB diskettes as 720KB (for the
Yamaha MDF-2 in this case) by taping over the sensing hole and using
the command prompt

 FORMAT A: /T:80 /N:9

If the diskette was previously formatted as 1.44MB, an error will occur
nonetheless and the formatting process halts.  The solution is to first
bulk erase the diskette with one of those large AC audio tape erasers.
45 out of 45 diskettes were successfully reformatted using this method.

Make sure to use opaque tape over the sensing hole since some drives
use optical detectors rather than mechanical switches.

Larry Doe