A preview version of Windows 8.1, codenamed Windows Blue, has been made available by Microsoft (NASDAQ: MSFT) for the desktop. Those looking to try out the beta, which Microsoft recommends for "experienced PC users only," can download the update by clicking here.

Windows 8.1 is a free update to Microsoft's Windows 8 and has also been called Windows Blue. The official update does not yet have a release date, but Microsoft says that Windows 8.1 will roll out to consumers "later this year." The update has reintroduced the "Start" button that Microsoft removed in the transition from Windows 7 to 8.

CEO Steve Ballmer gave the keynote speech at the Windows developer conference, called Microsoft Build 2013. Windows 8.1 is also expected to update the tablet and mobile devices that run on Microsoft's operating system.

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