Microsoft has now released Hyper-V to manufacturing (RTM).
A beta of Hyper-V was already included in Windows Server 2008, this update provides the final release of Hyper-V.

Download Hyper-V RTM 

More information about Hyper-V (Microsoft Virtualization product) can you find here:
http://www.microsoft.com/windowsserver2008/en/us/hyperv-main.aspx