Windows 7, as Microsoft’s fastest-selling OS in history, now has a release candidate for Service Pack 1 (SP1 RC). Alongside the SP1 RC for Windows 7, Microsoft also released the SP1 RC for Windows Server 2008 R2. Windows 7 and Windows Server 2008 R2 SP1 Release Candidate includes previous updates delivered over Windows Update as well as continuing incremental updates to the Windows 7 and Windows Server 2008 R2 platforms.
You must currently have the RTM version of Windows 7 or Windows Server 2008 R2 installed before you install the Release Candidate bits of both Windows 7 SP1 and Windows Server 2008 R2 SP1. You must also uninstall any Beta version of Service Pack 1 before you proceed with installing the newly released Release Candidate build.