i'd like to understand more about wmp album tagging

i sell 5 albums on itunes, but a search on wmp shows up only one.

Is there a way to update the main microsoft music database? where do they get their info from?
Does updating the info myself on wmp save it to the database or just locally?
Is there another db source to use in wmp to tag music?

I tried to access the site but it is restricted: