Operating system: Windows 2000, XP, VISTA, Mac OS X up to 10.5. Includes 20 pre-loaded songs. Uses 4 AA batteries (not included). Cannot play MP4 files, including content purchased through iTunes. iTunes users can convert non-digital rights management-protected MP4s into a playable MP3 format by choosing the files and selecting "Create MP3 version" from the right-click menu. Includes USB cable. For ages 3 and up. Thank you for looking.