How to manage a large music library in iTunes

I read only recently that a Music library can contain no more than 100,000 songs. I put 450,000 songs on an external hard drive and unchecked "Copy files to Music Media folder when adding to Library." Sync Library is off. I used "Add to library..." under Music File menu to add the contents of the external drive to the Music library. It took a couple of days, but the thousands of songs seem to be listed in the Music directory. But scrolling doesn't work, either with the cursor or with the gadget that scrolls rapidly if you grab it with the cursor; don't know what it is called. I scroll down the list of Genres, Artists, or Albums, but as soon as I stop scrolling the cursor with my finger on mouse, the list bounces back to the beginning. Can't create playlists because the lists keep bouncing around, out of control.

Suggestions appreciated. Can I divide my tunes up into four or five Libraries? Any way to control the behavior of the tune lists?

banjoboy54

[Re-Titled by Moderator]