I had the same problem and this method worked for me perfectly.
Thanks Mohican83!
This was a successful and much needed solution to my problem.

"Mohican83" wrote:

> The problem is the wmpfolders.wmdb is bad. Your Library is empty because
> windows doesn't know what folders to look for. The Monitoring folders dialog
> box must write to the wmpfolders.wmdb which is bogus if the library says
> empty.
>
> To repopulate the library.
> 1. Close Media Player(of course)
> 2. Open the %userprofile%\Application Data\Microsoft folder
> 3. RENAME the "Media Player" folder(I renamed mine to MediaPlayer)
> 4. Open the media player
> 5. Open the add to library dialog box
> 6. Your folders should now show. Close the box
> 7. Choose apply media information changes