1. Find the iTunes Music Library file. In Mac OS 9, this file is normally located in the iTunes folder in your Documents folder. In Mac OS X, the iTunes Music Library is located in either the Documents or Music folders. These folders are located in your Home folder; choose Home from the Finder's Go menu.

2. Drag the iTunes Music Library file to the Trash.

3. Optional: Find the "com.apple.iTunes.plist" file in your Preferences folder (~/Library/Preferences) and drag it to the Trash. This will reset your iTunes preferences, and cause the iTunes Setup Assistant to open so iTunes can search for all your music files again.

4. Open iTunes. A new iTunes Music Library file is created. You may need to recreate your playlists, and manually add music files back into your library.