There are 2 approaches to this.  The one you seem to be using is to first open Wordpad, then open the .cfg file.  To do this look in the drop down box (it's on the bottom of mine) and select it to show "All files (*.*).  All files will now be visible.

Another way is to click on a .cfg file and see what happens.  If you get a message that says "Windows cannot open this file" check the box that says "Select the program from a list" and OK.  You will then see a list of applications.

Leave the "Always open with this application" box checked if you're really sure otherwise it will work one time only.  Most people prefer to use Notepad for editing .cfg files.

MMM, the Scenery library IS helpful but doesn't answer my question regarding the .cfg file
The problem seems to be finding the file!!

Oops. I thought this was the FS9 forum & gave you the wrong link. Try this one. http://www.simviation.com/lair/fs2002sc.htm

No harm done as it's all basically the same.

ok, still can't find any .cfg files despite illuminating the hidden files. Where are they ??  There is an article entitled " Adding texture only files to Aircraft" which requires the opening of aircraft.cfg for example...