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Windows Server 2008 x64 Hyper-V RC1 Update - KB950049
This is the Hyper-V RC1 package for Windows Server 2008 x64. This package must be installed on Hyper-V server’s (physical machines). It includes the Hyper-V Server components for Full and Core installs, the Hyper-V Integration Components for Server 2008 x64 (see note below for RC1 improvements over RC0) and the Hyper-V Management Components for Full Windows installs.
Note This package is permanent. Once installed, it cannot be uninstalled. So you can’t got back to RC0 or Beta after installing RC1.
Tutto il resto alla Fonte: Hyper-V RC1 Release Available on Microsoft Download Center!