Are you certain it is not NTVDM error ?
I am running NV1 on xp pro and many of my customer are also and we all run full screen.
One of the problems is the command.com in the system32 dir could be the wrong version.
Another is the autoexec.nt and config.nt are missing or a line is wrong in these files.
They are also in the system32 dir.
Here are the contents of my 2 files.
Contents of autoexec.nt everything else is REM out
lh %SystemRoot%system32mscdexnt.exe
REM Install network redirector (load before dosx.exe)
lh %SystemRoot%system32redir
REM Install DPMI support
lh %SystemRoot%system32dosx
Contents of config.nt everything else is REM out
dos=high, umb
device=%SystemRoot%system32himem.sys
files=40
Thomas
