Install this update to enable Virtual Machine Manager 2008 Beta (VMM) to function with Release Candidate 1 (RC1) to the Hyper-V role. After you install this update, you may have to restart your computer. Once you have installed this update, it cannot be removed

Download: http://connect.microsoft.com

Note: Before installing this hotfix your Hyper-V needs to be RC1. With this update you cannot manage Hyper-V RC0 hosts.