I have installed fs2crew for pmdg 737 ngx few days back, but every time i hit the enable button there comes an error saying that : access to pmdg 737  ngx CFG file denied... what to do ? please help

thanks in advance.

Are you running with Admin privileges? Try running FS2Crew 737NGX as such.

What Rick said.

You have a write permission problem.

Right click on the FSX.exe or P3D.exe and select "always run as admin" in the compatibility tab.

This way FS2Crew should be able to add the required entries to the 737's panel.cfg file without being blocked.

 

FYI, this is also why it's a good reason to never install FSX/P3D into the program files folder.  It's best to install it to another location to help avoid write permission issues.