Here is an email I sent to Groovygamegear.com, after playing with the DOS uploader a little:

 Hi Randy,
Yesterday I tried to hook up my Keywiz Eco (1st version) to an old IBM
Intellistation desktop (P3 800) and to upload a custom layout with the
KWDOS3.EXE you provided me (see previous conversation).
Well it just didn't work, no matter what I tried (different PCs,
solutions below, etc.). It never found the Keywiz.
So I went back to the old kwdos.exe and it didn't work either. The
difference however was that after some hours of playing around I
finally managed to upload my layout. It turned out that there were two
culprits:

- a BIOS setting in the IBM Bios called "Keyboard Reset Delay" was
disabled - it had to be ENABLED. I haven't found any details on what
exactly this option means. It made no difference if I booted the PC
with the Keywiz attached or if I hotswapped it with the keyboard.

- since I have a German Windows 98SE installed, it loaded the keyb.com
TSR by default and seemingly this also prevented the utility from
working. Consequently KEYB can only be loaded AFTER KWDOS.EXE
regardless of using it in autoexec.bat or plain CLI.

Both old and new Windows uploaders were not affected by these settings
and worked fine. And like you said before, the CLI utility switches
the Keywiz to the custom layout by default, so sorry for my previous
questions.

Even if I don't think many users have a similar setup like me, you
might want to include these findings in your FAQ.

[...]

Thanks and best regards,
Martin