Randy.
The "Open With" option should work. In the "Open With" dialog choose your editor (Notepad?). Ensure that the checkmark "Always use the selected program..." is ticked, and click OK.
Double-clicking a .REG file should open your editor. You'll also note that the "Merge" action is replaced by "Open" in the context menu.
The above change applies to your user account only. You have to repeat the same in all other user accounts if you want.
Another option:
See:
Change Default Action of REG Files to “Edit.â€
http://www.aumha.org/regfiles.php
The editreg.reg in the above link, when merged, sets the (default) value and set it to "edit" in the following registry key:
[HKEY_CLASSES_ROOT\regfile\shell]
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Regards,
Ramesh Srinivasan, Microsoft MVP [Windows Shell/User]
Windows® Troubleshooting
http://www.winhelponline.com
Sorry Dave, you are close, but that only sets the default, it does not allow
one to change the ACTION taken when the program is double clicked.