How to find the IE9 View Source Editor registry key

Have you ever wondered where Internet Explorer looks for the registry key when you select to view the HTML page source of the page you are currently viewing? Or, has some application changed the default Notepad to something else, and you want it back?

Luckily, the solution is easy. Just look for the following registry key (on a 64-bit machine):

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\
Internet Explorer\View Source Editor\Editor Name

The "(Default)" value of this key is the full path used to launch the view source editor/viewer application. IE appends the current HTML file's cache path to the value you specify. For instance, to get Notepad back again, specify "C:\Windows\System32\Notepad.exe" as the value.

More details can be found here on MSDN. Oh, don't mind the screenshots that were taken from Internet Explorer 5 (IE5). The registry keys are still valid in IE9 (don't know about IE10, though).