IE gone bezirk: no source view

[TomJ]

I do most of my browsing using Firefox, but for my web development I check my results in Internet Explorer to.
But recently I have discovered a remarkable phenomenon: whenever I want to view the source of my html page, IE is unable to find the proper application to do so. In the IE options, Notepad is clearly marked; whenever I double click a TXT file, Windows will open Notepad without hesitation, so Notepad IS available. But IE apparently has lost its clues.
In stead of activating Notepad, it shows the root of my C-disk in a Explorer window. Whether I call for a source view from the context menu or from the main View menu.

Anyone any suggestions?

[The Old Sarge]

Have you tried it on another computer?

I just called up several sites on IE and all showed just fine.

[TomJ]

This feature is confined to one computer. My office computer works fine. But since it is my office computer, it is no use to me at home. And I only have one computer at home.
I am pretty sure it must have been a setting I altered myself (in ignorance and/or stupidity), but I cannot recollect what / where / which / when, let alone why.
And particularly what I could do to undo it.

[TomJ]

Through a hint I got somewhere else, I decided to check the Registry and found the reference to an editor for IE to be completely blank.
After recreating the link to Notepad, IE behaved as well as can be expected.
Thank you for your patience.
[closed]