Hyper-V Generation 2 Virtual Machine Compatibility

Q: Will the new Generation 2 virtual machines in Windows Server 2012 R2 Hyper-V be usable by Windows Server 2008 R2 and Windows 7?

A: The new Generation 2 (G2) virtual machines (VMs) are based on UEFI,while the old Generation 1 machines are BIOS based. Because of the requirement of full native UEFI support, Windows 2008 R2 and Windows 7 can't run in a Generation 2 VM. Only Windows Server 2012 and Windows 8 and above can run in a Generation 2 VM and only the 64-bit (x64) versions can run in a Generation 2 VM.