As it turns out, the new implementation of UEFI for guests in Hyper-V 2012 R2 requires a GPT disk with an EFI system partition on it.
What does this mean to the average sys admin loaded with PowerShell scripts who wish to deploy VM’s using the new “Generation 2” feature of Hyper-V 2012 R2? It means your existing VHD provisioning scripts don’t work for Generation 2 guests.
When I regain my sanity, I’ll might publish a code snippet on handling that type of a deployment. In the meantime, going back to evaluating Hyper-V 2012 R2 before the BUILD conference.