Were there any OneNote files in these folders or just a bunch of other
files (text files, etc.)?

OneNote won't convert these files into OneNote sections automatically.
That option in Explorer to open a folder as a Notebook is intended as a way
to reopen a previously closed Notebook, not to convert the contents into a
new Notebook.

=?Utf-8?B?SW9uYQ==?= <Iona@discussions.microsoft.com> wrote in
news:D1335306-716C-4B13-9114-4F8DA788F3DF@microsoft.com:

> I’ve been a user from the get-go, and the early single notebook
> provided me a place for everything with everything in its place. Until
> today. I decided that it was time to dump many of my research files
> (MS Word 1994-2007) into OneNote 2007 and make it my trusted system.
> Here’s what I did:
>
> In Windows Explorer, I opened a folder as a Notebook in OneNote.
> Thankfully, I made a copy first. The folder consisted of 65
> sub-folders, 829 files comprising 61.5 MB. About 90 percent of these
> files are text. Voila! Outlook did what it said it would do, and off I
> went to OneNote. My new notebook had taken my sub-folders and all the
> files and created Section Groups that I’ve been unable to open, take
> a peek inside, or resuscitate.
>
> Before I abandon OneNote’s research capabilities, please tell me
> what might have happened and what, if anything, I can do about it.
>
> Thank you,
>
>
>