Lost Folders created in Windows Live Mail

I created a folder in Windows Live Mail with about six subfolders.

I was able to use these folders daily for about two years.

I was able to export and import them between my laptop and desktop computers.

They behaved exactly as the folders provided with the original equipment (Dell Inspiron 1545).

After some two years of constant, daily  use, the main folder simply disappeared with all its subfolders (along with two years of work).

I have read the saved threads with this same title to no avail.

Can you help?