Windows 10 Hyper-V has exclusive access to VT-X extensions by default

[shmooly413]

Talked briefly on twitter, figured i'd give you the full details
Error Generated on Windows 10 x64 Home

2017/02/18 10:35:58 ui error: Build 'virtualbox-iso' errored: Error starting VM: VBoxManage error: VBoxManage.exe: error: The virtual machine 'packer-virtualbox-iso-1487439296' has terminated unexpectedly during startup with exit code 1 (0x1).  More details may be available in 'C:\Users\\VirtualBox VMs\packer-virtualbox-iso-1487439296\Logs\VBoxHardening.log'
VBoxManage.exe: error: Details: code E_FAIL (0x80004005), component MachineWrap, interface IMachine

Cause:
Windows 10 Hyper-v controls VT-x by default and does not share that control.
http://stackoverflow.com/questions/37955942/vagrant-up-vboxmanage-exe-error-vt-x-is-not-available-verr-vmx-no-vmx-code

Solution:
Use bcdedit /set hypervisorlaunchtype off then reboot your machine, to use Hyper-V again, simply (or auto bcdedit /set hypervisorlaunchtype on and reboot your computer again
https://blogs.technet.microsoft.com/gmarchetti/2008/12/07/turning-hyper-v-on-and-off/

[obilodeau]

Thanks for the instructions! I'll integrate those in the README and the references in the documentation.

[filinpavel]

Since version 6 of Virtualbox it supports using Hyper-V as the fallback execution core (Changelog)