Microsoft have been trying to get into the portable music player business for some time now, since 2003 when they launched their Portal Media Center OS for handheld devices, and the ‘Plays for Sure’ initiative to guarantee compatibility between devices bearing this logo and Windows and WMA format files.
They have not made any significant dent in the market yet. iPod are still dominating, even though there is a whole range of other (non-Microsoft as well as Microsoft backed) devices out there to choose from, all shapes and sizes, some with flash memory, some taking flash cards, and some with integral harddrives.
This article on RegHardware suggests Microsoft’s next attempt may be to launch a portable game console to compete with Nintendo and Sony that may also play movies and music.