When I click on "select native units" I get the attached screen.  This screen indicates to me that it has nothing to do with my problem.
Am I wrong?

Please attach your xml.
Hood

Edit
I see you attached it in another post, I have also answered in that post.

I also get this message but if I hit OK, I have another message box like the one on the second image.

Jeff

When I do that everything is screwed up.

From reading all your postings on this it appears you have Mach set up in metric units not imperial.
May be a good idea to save your .xml and settings so you can always go back but start afresh re-install Mach and set it up in imperial units right from the start.

Tweakie.

I am sure I am setup in inches.  I wrote a program to do a 2 inch square at 1/8 inch deep.  The resulting square is 2 inches by 2 inches and 1.8 inch deep.  I only have a problem if I include the command g20 in my code.  When I do this the units change to something other than inches.   

Your xml showed you were set up in metric units.
Hood

If you are trying to learn how to use your new machine and you wish to use imperial units then Mach should really be set-up in imperial units.

Yes you may have to redo your motor steps but this is not rocket science and getting everything right now will save you lots of grief and configuration problems in the future not to mention possible problems with imported GCode from other programs.

Tweakie.