Windows 7 has been leaked online, as pre-CES murmurings suggest Microsoft boss Steve Ballmer will unveil more about the new software in his keynote at the January show.

A beta version, "Build 7000", of Microsoft's next operating system can be found on peer-to-peer network BitTorrent, available for anyone to download.

Windows 7 is not due to launch until 2010, although rumours have suggested a Christmas 2009 debut is not out of the question.

Microsoft recently extended the shelf life of XP, its pre-Vista operating system, a move thought to be due to customer demand from those hoping to skip Vista and move straight to Windows 7.