http://www.nytimes.com/2006/03/09/technology/circuits/09pogue.html
Like almost all non-iPod music players, the Z5 is based on Microsoft's music-player software. That is, it doesn't work with the Macintosh. And while the Z5 can't play songs from Apple's iTunes Music Store, it can play songs from Rhapsody, Napster, Musicmatch, MSN Music, Wal-Mart, AOL Music Now, Yahoo Music and other members of the "MMS-MMS" consortium (Microsoft-based Music Stores with Minuscule Market Share).