I was having this same problem recently. I read through here and tried uninstalling my keyboard, turning the WMP to manual, ect.
None of what I tried worked.
Then I went into the Options menu under Tools (If you dont know much about computers, you can right click the bar at the top of your screen and select "Show menu bar" if you cant see the Tools menu) I turned off a few default options:
-Add remote media files to library when played - Under Player
-Display media information from internet - Under Privacy
-Update music files by retrieving information from the internet - Under Privacy
-Download usage rights when I play or sync a file - Under Privacy
-Automatically check if protected files need to be refreshed - Under Privacy
-Retrieve additional information from the internet - Under Library
Mostly because I don't like my applications sending/receiving information without my approval ANYWAY.
As soon as I clicked apply and closed the window... no more popping up.
I'm not positive all of these options need to be changed to stop this from occurring but this worked for me and I didn't feel like trying them all 1 at a time to find the magic combination.