You can download the latest build of Microsoft Windows 8 from windows.microsoft.com/en-US/windows-8/download . Keep in mind that you can download a SETUP or an .ISO. Personally, I would only work with the .ISO on a fresh harddrive (or fresh partition 🙂 ) The CD key for this is TK8TP-9JN6P-7X7WW-RFFTV-B7QPF
And if you are wondering “can I upgrade Windows 8 Consumer Preview to this Windows 8 Release Preview”, the answer is yes. See windows.microsoft.com/en-US/windows-8/faq for details
The support for this build is web only (unless you are on the private invite list). You can post your comments and hope for a response answers.microsoft.com/en-us/windows/forum/windows_8?auth=1
With comments like “I don’t expect it to silence the skeptics who think that the Metro-izing of Windows is a strategic blunder, a franchise killer that deserves a place alongside epic failures like New Coke and Star Wars: Episode 1. But if you’ve managed to retain an open mind about Windows 8, the Release Preview goes a long way toward making sense of Windows 8’s controversial design decisions…” from Windows 8 dev staff, I think we can safely say they are getting the message that Metro without a Start Button is a very risky proposition.
Windows 2012 Server RC is available only to MSDN and Technet subscribers. So if you have an account surf over to www.microsoft.com/technet and get it.