“Windows 7 and Windows Server 2008 R2 SP1 Beta helps keep your PCs and servers on the latest support level, provides ongoing improvements to the Windows Operating System (OS), by including previous updates delivered over Windows Update as well as continuing incremental updates to the Windows 7 and Windows Server 2008 R2 platforms based on customer and partner feedback, and is easy for organizations to deploy a single set of updates.”
In order to download and install the Windows 7 and Windows Server 2008 R2 SP1 Beta you must currently have a Release to Manufacturing (RTM) version of Windows 7 and Windows Server 2008 R2 already installed.
Please Note: This early release of Windows 7 and Windows Server 2008 R2 SP1 Beta is not available for home users. The SP1 Beta does not provide new end-user features, and installation is not supported by Microsoft.
You can register and download it from http://technet.microsoft.com/hi-in/evalcenter/ff183870.aspx
It is available as -
32-bit (x86) Edition using Windows Update
64-bit (x64) Edition using Windows Update
1.2GB ISO file with standalone update (The download is a unified ISO including 32 bit SP1 Update for Windows 7 and the 64 bit update for both Windows 7 and Windows Server 2008 R2.)
For Documentation related to Hotfixes, security updates, notable changes, FAQs , please check -