I know how to use WinExec or CreateProcess to run an application. I can also use CreateProcess to open a specific file name within an anpplication.

What I want, is to open a file that is associated with a specific application, but I don't know the command line or the application installation directory.

For insance, assume that .txt is associated with another application instead of notepad. Now, when I doubleclick on a text file, is opened by that application rather than notepad.

All that I want, opening a file with the application that file is associated, but I don't know the application.