However, now when I try to open iTunes it immediately says, "The File 'iTunes Library' cannot be read because it was created by a newer version of iTunes." If you decide to downgrade iTunes, there are ...

The iTunes 7.3 application (located in /Applications) com.apple.iTunes.plist (from ~/Library/Preferences) iTunes.pkg (from /Library/Receipts) iTunesX.pkg (from /Library/Receipts) then re-installing ...