Since no one responded to my post, I am --for anyone else having the
same problem -- posting the solution I finally found. The problem was
that suddenly I could no longer left-click-open certain documents,
notably htm/html files. I was forced to first open the browser and
open the document via the browser menu. When I right-clicked on an
htm file, the context menu did not offer the "Open with" option.
Folder Options rebuffed me, saying the htm/html extensions were
assigned to Netscape; it would not let me edit those file
associations. I don't have (nor do I want) Netscape browseri
nstalled, so the files could not open in Netscape.

Here's the fix that worked: Select an htm document, and then hold
down the shift key while right-clicking. This brings up a context
menu that does have the "Open with" option. On the program list that
came up, I selected Internet Explorer, checked the box that said
"Always use this program to open this kind of file" and then clicked
"OK."

So far, so good. I can once again click-open htm & html documents
without having to go the long way of starting up the browser and
opening the file from the menu.