Windows: List and Launch applications associated with an extension

Question

How to determine the applications associated with a particular extension (e.g. .JPG) and then determine where the executable to that application is located so that it can be

Answer 1

Also HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\

.EXT\OpenWithList key for the "Open width..." list ('a', 'b', 'c', 'd' etc string values for the choices)

.EXT\UserChoice key for the "Always use the selected program to open this kind of file" ('Progid' string value value)

All values are keys, used the same way as docName in the example above.