Apparently Microsoft is currently preparing a pre-release version of Windows 8 to release next month.
The build number is apparently Build 8064.0.FBL 110806.
Chinese site PCBeta revealed an 8064 build of Windows 8, built on August 6. The build is part of Microsoft’s preparations for its BUILD conference next month.
PCBeta also posted a setup screenshot (below) that indicates the build is a “Developer Preview” instead of a beta.
Microsoft was expected to supply an early beta copy of Windows 8 during BUILD, a schedule that would mark a shift from the earlier Windows 7 development cycle.
If the version of Windows 8 is only a developer preview then that might mean we should expect the Windows 8 Beta sometime next year.
This is of course just speculation and we should know more at BUILD.