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I've upgraded to Windows 8 some weeks ago (MSDNAA!) and today, while I was trying to run a VM, I've noticed that VT-x is disabled.

Now, Hyper-V works without problems, as I've tried emulating Win7 and WP8; but VirtualBox says that VT-x is disabled and it can't run my VM.

Just to double check, I've run Securable by GRC and the Intel utility and both says that I've got VT-x off.

Here comes the problem:
VT-x is ON in my BIOS, and it worked flawlessly before upgrading to Windows 8!

Any kind of suggestion?

EDIT: My CPU supports VT-x: http://ark.intel.com/products/52219

Hennes
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StepTNT
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3 Answers3

32

Had same issue. I enabled the Hyper-V to test the built-in virtualization in Windows 8 and that caused the OS to report Vt-x incorrectly.

I disabled Hyper-V from the Windows features and now VT-x is enabled again.

Go to Control Panel → Programs and Features → Turn Windows features On or Off and then uncheck Hyper-V.

Oliver Salzburg
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ClearLogic
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  • Are you saying that there's some kind of bug that stops me from having both Hyper-V and Virtualbox running? That's weird! I'll try to see if your solution works – StepTNT Nov 20 '12 at 18:37
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    weird but real. It worked for me too – David Apr 18 '13 at 20:05
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    This isn't a bug - it's just a consequence of how Windows 8 runs on HyperV. When you enable the HyperV feature, you actually install HyperV as the host OS (hypervisor) and change your existing Windows 8 installation into a special (guest) OS running on HyperV. – Jeff Meatball Yang Jul 06 '13 at 05:29
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    This also solved the problem for me. I feel like this should be made more obvious in Windows 8 when installing the hyper-V option. Alternately, I think the VirtualBox guys could be more clear about this potential edge case in their manual where they discuss enabling VT-x – Chris Aug 26 '13 at 20:05
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    Oh my god, spend last 4 days looking for an answer of this strange behavour. I must have enabled Hyper-V and then forgot about it. I was trying to figure out what caused this problem. Thank you! I've also had problems with internet connectivity recently. I'll research whether Hyper-V with VirtualBox clash caused that as well. – VsMaX Sep 03 '13 at 14:19
  • instead of completely uninstalling Hyper-V, you could create separate hardware profiles (using `bcdedit`) with hypervisor enabled/disabled, and choose at boot-time which one to use: http://derekgusoff.wordpress.com/2012/09/05/run-hyper-v-and-virtualbox-on-the-same-machine/ – Amro Sep 09 '13 at 21:49
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    Thanks man. I checked the BIOS settings over and over again but it was Hyper-V that caused the problem. – Tom Oct 16 '13 at 09:38
  • @JeffMeatballYang Is there a technet site where I can read about this? – Tom Oct 16 '13 at 09:40
  • Almost thought I'd bought the wrong processor! This saved my skin, thanks! (Also works with Windows 10) – SoftDeveloper Mar 04 '16 at 11:05
1

First, check if VT-x enabled in BIOS\UEFI Second, disable Hyper-V:

dism.exe /Online /Disable-Feature:Microsoft-Hyper-V

Here is detailed instruction: http://druss.co/2015/06/fix-vt-x-is-not-available-verr_vmx_no_vmx-in-virtualbox/

druss
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0

I found this article/post on Intel's site. Given that for this person, a clean install of Windows 8 (ignoring the fact that this was before the proper release,) I would suggest doing the same.

I have seen no end of problems lately for people who upgraded, which a clean install fixed.

Windos
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