Microsoft has just finished its latest virtualization project they call "Hyper-V Server 2008" and it's freely available for download here.

Hyper-V was built using Windows hypervisor and harnesses the Windows Server driver model and virtualization components to run anything from Linux distributions to Windows XP, Vista and Server 2000, 2003 and 2008. It's also available in multiple language formats.

You can learn more about it here folks.