I've already run the register.exe before my last post. I did it a couple more times. Finished successfully twice, shows P3D v3 installed, shows adding HyperGauge to P3D v3, but the C172 is not installed in v3 SimObjects --> Airplanes. Ran register.exe again and got this error message:
"Error 527 extracting HyperGauge to Flight Simulator P3D(v3) folder H:\Program Files (x86)\Lockheed Martin\Pepar3Dv3\Modules. Code: 527." I did check this path and HyperGuage.dll is installed here.
Sorry to be a pain. What am I missing here?