Windows 7 and Windows Server 2008 R2 SP1 Release Candidate 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.

32-bit | 64-bit

DVD ISO
(This DVD ISO disk image contains the standalone update packages for the public release candidate.)

32-bit Windows Update Sign Up Tool | 64-bit Windows Update Sign Up Tool
(This tool enables your 32-bit or 64-bit Windows 7 or Windows Server 2008 R2 machine to participate in the public beta via Windows Update. Run this tool and then check for updates in Windows Update.)

Windows 7 and Windows Server 2008 R2 SP1 Release Candidate FAQ

More info