4DOS is only a command processor and makes no fundamental changes to DOS.
In 10+ years of beta testing & using 4DOS, I have VERY rarely come across a
compability problem related to it. Those I have found are 99% to do with
batch files, not executables. One place I have occasionally found to be an
issue is path length: 4DOS permits the path (and environment variables in
general) to be longer than the 127 character limit imposed by MS-DOS. Some
compilers, as part of their standard start-up code, place a copy of the
environment on the stack and overlong variables do occasionally cause
problems. Ray, you should check your PATH to see if it exceeds 127
characters and, if so, try running selfold with a shorter path to see if
that fixes the problem.
- DaveL