A while back, someone posted a message about the lack of support
they received from Microsoft for DOS 5.0.  The ham mentioned that
DOS 5.0 was purchased as a complete or full package. And MS support
essentially told the ham that no support can be given for it.

That's probably true.  As far as I'm aware, the Microsoft OS product
line for DOS 5.0 is only the "upgrade" package. There is no complete
or full MS-DOS 5.0 package available from Microsoft.  For that, one 
would buy the IBM package (Big Blue's DOS 5 product line includes
both the "upgrade" and the complete or full package) or from an OEM.

However, as I understood it, the complete package from an OEM may
not be supported by MS because the OEM package is supposed to be
sold as part of a computer system and support should be obtained
from the dealer from which the system was purchased from.

Kinda hokey but it looks like that's how the game is being played.
For example, I recently purchased a few computer systems from
Gateway 2000 for my employer.  Gateway supplies MS-DOS 5.0 and
Windows 3 with their systems.  The diskettes and manuals supplied
indicates that I've got a complete or full package. But if I need
technical support, according to Gateway, I call Gateway's tech
support, not Microsoft (of course, I won't necessarily do this
if I do run into a problem :) ).

The DOS "tech support" at MS have probably been told that if it ain't
a MS-DOS 5.0 "upgrade", it ain't supported.  Confuses the peanuts
out of everyone.  73 es watch out when you're at the swap meet.

de Gary N6MMM @ W6QFK.#SOCA.CA