A Microsoft technical support document has shown that its Zune media player will not be compatible with Windows Vista. 

The posting also shows that Zune users will have to upgrade their operating system if they are not using Windows XP or Windows Media Centre. Early versions of Media Centre are also incompatible with the player.

"Windows Vista is not supported at this time," the site reads. "Check back soon for updates."

The leak will cast further doubt on the short-term success of the Zune player.

Apple chief executive Steve Jobs has already dismissed the player as "no threat" to iPod sales, and Microsoft's own staff have gone on record with the prediction that Microsoft will not make money on the device for at least three years.