You can also use the My Movie Database Views, which will give you a combined view of the movies (or music, there it is the same) of everything (for example by Genre, Year, Artist etc.)
Now, one other question, is it just me/my pc, or is it s-l-o-w to load folders?!
I have about 250 movies in avi format stored on a NAS box - windows explorer opens them in about 2 seconds but MP takes about 30-45, sometimes more
(note: They are in list view so not fetching any previews or anything)