How to disable Hyper-V for gaming:
1) Stop all my Virtual Machines and close Hyper-V2) Set the "Hyper-V Virtual Machine Management" service to disabled3) Open an elevated cmd prompt and type: "bcdedit /set hypervisorlaunchtype off"4) Restart
Make available again:
BCDEDIT /set hypervisorlaunchtype auto
More information how to resolve problem: "Hyper-V 2008: Troubleshooting Event ID 3112 "The virtual machine could not be started because the hypervisor is not running."
http://social.technet.microsoft.com/wiki/contents/articles/194.hyper-v-2008-troubleshooting-event-id-3112-the-virtual-machine-could-not-be-started-because-the-hypervisor-is-not-running.aspx