Akai S1000 / S1100 samplers

Hello. I own an S1100 with its original operative system (1.36) and I
would like to upgrade to 4.3. I downloaded the update file from the
akai website (the one that asks for a blank diskette) but I really
can't be able to make it work... I tried it in Windows XP, 95 (MS-DOS
prompt) and various versions of DOS but the program always quits
saying "Diskette error - try another" whatever disk format or density
I use, both formatted in DOS and in AKAI format with the S1100 itself
and also with Akaidisk. Not to mention that I tried with 10 different
floppy disks...
Did anyone else experienced this problem?
Is there any sysex version of OS 4.3 so I can upgrade via midi?
Thanks
David