Paul,
FWIW, when DOS 5 first came out there were a number of systems (and
there did not seem to be any rhyme or reason) for which SETVER didn't work
under genuine MS DOS. I saw it myself on a Unisys PC, but there were many such
reports here. Fortunately MSCDEX 2.21 which accepts 5 as a valid version number
(but still won't accept 6, the current DR DOS version<g>) fixed those machines.
Frank