Hyper-V !

https://blogs.technet.com/stbnewsbytes/archive/2008/06/26/it-s-here-windows-server-2008-hyper-v-is-available-for-download.aspx 

NeedI say more, but of course you know this already :-)

 Also: https://blogs.technet.com/virtualization/archive/2008/06/26/wu-hoo-only-12-days-to-wu.aspx or

https://blogs.technet.com/windowsserver/archive/2008/06/25/microsoft-com-powered-by-hyper-v.aspx