Microsoft has released the latest version of their Windows product called as Windows 8 and it is in RELEASE PREVIEW now. Release Preview is actually a Release Candidate build, just some changes to the terminologies.
Windows 8 Release Preview is available for download through http://windows.microsoft.com/en-US/windows-8/release-preview and MSDN Subscribers can download from the MSDN Subscription downloads.
Go through the introduction at http://windows.microsoft.com/en-US/windows-8/release-preview .
Read the Windows 8 team blog http://blogs.msdn.com/b/b8/archive/2012/05/31/delivering-the-windows-8-release-preview.aspx
Extracted from Windows Team Blog
Microsoft will roll out the Windows Upgrade Offer in 131 markets including the US and Canada. Consumers who purchase eligible Windows 7 PCs that are preinstalled with Windows 7 Home Basic, Home Premium, Professional, or Ultimate and include a matching and valid OEM Certificate of Authenticity through January 31, 2013 will be able to purchase an upgrade to Windows 8 Pro for $14.99 (U.S.) which will be redeemable when Windows 8 is generally available (the program expires in February 2013). For more on the editions of Windows 8, see this blog post. When consumers register for the Windows Upgrade Offer, they will be able to download Windows 8 Pro starting the day it’s made generally available and the upgrade comes with 90 days of support from Microsoft.
Download Links from Microsoft