iTunes 2: Cannot Add MP3 Files to Library By Dragging Them to iTunes Window
To add MP3 files to iTunes 2 in Mac OS X (Simplified Chinese), choose Add to Library from the File menu instead of dragging the file to the iTunes window.
Symptom
You may not be able to add MP3 files to the music library by dragging them in to the iTunes window.
Solution
Choose Add to Library from the File menu instead of dragging the files or folders to the iTunes window.