You can use a 1.44Mbyte _drive_ with 720K _disks_ on a
XT controller,
though. It's a bit of a waste of the drive, but since 720K-only drives
are not common any more, you might have to do this. Using 1.44Mbyte disks
will probably prove unreliable, even though you'll only be formatting
them for 720K.
I've got a load of 720k disks from a dumpster-diving evening (woowoo, I
also got a clock :) ). Yours for shipping. I'd guess somewhere around
50-100 of them, though I haven't really seperated them from the 1.44
ones... I almost never use disks except to boot OSs and install them, so I
have them all in a box in the corner of my basement... I tend to make a
pile of 720k disks when I find them.
Kevin