If this is a WinForms application, then the file app.config never makes it out of the door! It's copied by the build process (to
that's what gets deployed with (and used by) your application when it runs for real.
That said, after you've installed your application on your users machine, they almost certainly
won't be able to update the your-program-name.exe.config file anyway! One of the "Joys" of U.A.C. is that everything under C:\Program Files* is
read-only to regular users so any attempt to write into this area will fail.
I'd suggest you need to find somewhere else to persist these settings.