Cannot link My Documents to Library\Documents

I have four computers running “identical” (obviously not) configurations of 32-bit Windows 7 Home Premium. All W7 updates are applied to each. I have all my dynamic data on a local network on a D-Link DNS-323 in a folder named My Documents.

Here’s the “obviously not” problem. On one, I cannot install My Documents in the Library\Documents folder. If I click on Documents I get the message “Documents is empty” “No folders have been included in the library”. If I continue by clicking on “Include a folder” and then select My Documents, I get a message “This network location can’t be included because it is not indexed”.

Three computers included it without a hitch. This one refuses. Has anyone an idea of what is going on, or where to look?

Thanks.

After fighting this for a few days and doing fruitless searches I finally set up the right search and came up with this:

How to properly add a network shared folder to a Library in Windows • PUREinfoTech

But.... when I went to test it, somehow My Documents had already become linked. ????? How and when I do not know.

So I will tentatively mark this as solved with a caution that I did not actually try it.