Jerry,
I have uploaded my test project for you and some screenshots:
http://www.lindersoft.com/projects/cat_ev.zip
It adds a "c:\cat123" folder to the PATH environment variable. Tested on Windows XP, Windows 7, Windows 8, Windows 8.1 and Windows 10. The installer always created the correct and expected registry value data for the PATH value name.
Can you manipulate the project in such a way that it "fails"?
Friedrich