The Windows Phone Emulator couldn't start because they hypervisor isn't running

=============== Error One ==============
The Windows Phone Emulator couldn't start because they hypervisor isn't running.
The likely cause is that the hardware-assisted virtualization isn't turned on.

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Solution
1- go to BIOS and chanage virtualization to True
2- add Hyper-v to Your window if it not found (add features to windows 8.1)
3- active Hyper-v from control panel