If the ONLY problems are "Incorrect DOS Version" messages, then you can
still use 6.22 . That's what SETVER is for. Somewhere in the code that
you are running is something that closely resembles:
MOV AH, 30h
INT 21h
CMP AX, ...
That inquires of the OS what version it is, and then balks if it isn't
what was expected. SETVER, which started with version 5.00 (?) lets the
OS lie about its age for just that situation. SETVER contains a database
that is configurable via the command line, so that the OS can keep its
lies straight. You'll need to install SETVER and add entry to its
database.