Utilities to configure file associations in Windows Explorer

Windows Explorer already has an interface for customizing the file associations for the different file types. See Customize the right-click menu in Windows Explorer.
The default Windows Explorer file type editor is rather limited (especially in Vista/Win7 where you can’t change the behavior of the edit or play context menu options). Instead one can consider a 3rd party file association editor, that allows editing of even special file types like All Files, Unknown Files, Drives etc.

Modify the context menu with manual registry editing

If everything fails, then one can also adventure directly into the registry database to fix file-type association:

  1. Open the Registry Editor (regedit.exe) and go the registry-key matching the file-extension (ex. .txt):


    The (Default) value below this registry-key will specify a logical name (ex. txtfile) or an application name.

    The use of a logical name is smart when multiple file-extensions (text and txt) should have the same context menu, then it is just a matter of making them point to the same logical name.

  2. Browse to the registry-key specified with the logical name (ex. txtfile):

    [HKEY_CLASSES_ROOT \txtfile] Below this registry key there is a shell folder, and all available commands for this logical name are listed there. One can then add, modify or remove commands from that list.

More Info MSDN - Extending Shortcut Menus