Microsoft has started giving Original Design Manufacturer (ODMs) and Original Equipment Manufacturers (OEMs) access to early Windows 8 builds. The software giant has already posted Windows 8 build 7971 on Microsoft Connect under "Windows 8 and Server vNext Pre-Release Program." The build string is "7971.0.110324-1900" which means the build is quite recent as it was compiled on March 24, 2011 at 7:00 PM.
It follows that certain departments at these companies are starting to test Windows 8. This does not mean, however, that a Windows 8 build is anywhere near ready or that you will be able to get access to the program on Microsoft Connect. In fact, while the testing website always requires an invitation code, they are unique this time around, meaning they can only be used once.
The above screenshot, which is reportedly for installing the aforementioned build, is from My Digital Life forums. It really doesn't show much, but it does promise that more screenshots are bound to be posted, not to mention an actual build will likely leak soon as well.
Windows 8 Milestone 1 screenshots leaked earlier this year. Windows 8 Milestone 2 was rumored to be compiled two months ago and screenshots of one of the builds leaked earlier this month. It's been suggested that this most recent build of Windows 8 is from Milestone 3 and that is why Microsoft has deemed it ready for its partners.