Hello,
After searching my computer for those files, I was able to locate expdaqmx.chm in two locations:
C:\Program Files\National Instruments\LabVIEW 7.0\help\
C:\Program Files\National Instruments\LabVIEW 7.1\help\
This file should have been installed in your LabVIEW help\ directory when you installed the DAQmx API. If it's not there, you have three options:
1) Try a repair on NI-DAQmx
2) Reinstall NI-DAQmx
3) Try to use the expdaqmx.chm file that I am attaching to this post.
Best of luck.
Jared A.