A prerelease development milestone of Windows 8 belonging to the Beta stage is already being tested by some early adopters, seem suggest some recently leaked screenshots.
One of the images included with this article, courtesy of MDL, has been snapped during the boot process, when the tester needed to select which operating system to launch, Windows 8 Beta, or Windows Server 8 Standard Beta.
The second screenshot reveals that Windows Media Center will be included into Windows 8 Beta.
Windows 8 Beta Already Being Tested, Suggest Leaked Screenshots - Softpedia