This worked on my machine and a collegues, it seems to resolve all environmental nmake errors.
Exit xmath, sysbld, etc...
Find your vsvars32.bat (C:\Program Files\Microsoft Visual Studio .NET 2003\Common7\Tools)
Find your xmath.bat or matrixx.bat, depending on your version (C:\Program Files\National Instruments\MATRIXx\bin)
Open vsvars32.bat in a text editor and copy its entire contents
Open xmath.bat in a text editor and paste the entire contents of the vsvar32.bat on the line prior to the version line (
set
MTXVER=7.1.8)
Save the xmath.bat
From now on to start up xmath, double click on the bat file.
The environmental variable are set each time and I found that all errors were extinguished.
This worked on MatrixX 7.1.6 and with Visual Studio 2003 and 2005