Hyper-V

Microsoft Hyper-V, codenamed Viridian^[5] and formerly known as Windows Server Virtualization, is a hypervisor-based virtualization system for x86-64 systems.^[6] A beta version of Hyper-V was shipped with certain x86-64 editions of Windows Server 2008, and the finalized version (automatically updated through Windows Update) was released on June 26, 2008.^[7] Hyper-V has since been released in a free stand-alone version, and has been upgraded to Release 2 (R2) status.
microsoft.com/spain/windowsserver2008/virtualization/hyperv
blogs.technet.com/b/davidcervigon/.../hyper-v-y-antivirus
vmware.com/.../True_Cost_Virtual_Server_Solutions.pdf
Microsoft's Hyper-V R2 vs. VMware's vSphere: A cost comparison
2007 The Price? $28!