change application associated with an extension

Solution 1:

You can use something like FileTypesMan to accomplish this.

1. Select the file type/extension you want to edit:

   

2. Right-click it and save all details to a text file for future reference (if you want to revert)

3. Select all the Actions shown for that file type in the bottom pane, right-click and save the details to a text file as well

4. Now from the bottom pane edit the open action (via right-click/context menu or F3) and modify the Command-Line as required to launch an alternate viewer/editor:

   

5. Similarly edit other actions as required

6. Next edit the selected file type from the top pane (via right-click/context menu or F2) and ensure the Description, Default Icon etc. are unaffected and remain the same as before:

   

7. Exit FileTypesMan, log off and log back in or reboot as required, then test your changes

Of course you can do all this from the registry as well, but this utility just makes it easier (and likely safer too). :)