I can't start any VMs any more!? (Windows 10 Home) - SOLVED

[yrro]

After booting up my Windows machine this morning (running Windows 10 Home 2004) I can't start any VirtualBox VMs any more.

I'm running VirtualBox 6.1.

Here is the error from VirtualBox:

WHvCapabilityCodeHypervisorPresent is FALSE! Make sure you have enabled the 'Windows Hypervisor Platform' feature. (VERR_NEM_NOT_AVAILABLE).
VT-x is not available (VERR_VMX_NO_VMX).

Result Code:
E_FAIL (0x80004005)
Component:
ConsoleWrap
Interface:
IConsole {872da645-4a9b-1727-bee2-5585105b9eed}

There's a lot on the web about these sorts of error but they invariably talk about disabling Hyper-V. But I have Windows 10 Home - Hyper-V is not available in this SKU!

I have also noticed two curious changes in VirtualBox's UI:

First, I can't change the settings of any VMs:

Invalid settings detected
System Acceleration page: The hardware virtualization is enabled in the Acceleration section of the System page although it is not supported by the host system. It should be disabled in order to start the virtual system.

Seems pretty obvious what I should do right? Well there are only two options on the Acceleration section.

Paravirtualization Interface which is set to KVM. It's a drop-down list. I have tried every option in there any it doesn't cause the 'Invalid settings detected' condition to clear.

The other setting is the checkbox for Nested Paging. Likewise, toggling this doesn't help.

Secondly, when trying to make a new VM I have noticed that all the 64-bit options have disappeared.

Now I know what you're thinking, this idiot must have disabled VT-x in his BIOS settings. Well I haven't, honest! When I fire up task manager in the Performance section it confirms 'Virtualization: Enabled'.

And when I run systeminfo, it outputs:

Hyper-V Requirements: A hypervisor has been detected. Features required for Hyper-V will not be displayed.

... which may be a significant clue for someone who knows how all this plumbing is tied together on Windows...

[yrro]

Solved and yes I was in fact an idiot all along.

Turns out at some point I had enabled Hyper-V on the command line with:

Code: Select all

dism.exe /online /enable-feature /featurename:VirtualMachinePlatform /all /norestart

... just to see if WSLv2 could be used on Windows 10 Home. But since I didn't want to reboot to test it straight away, I forgot I had done so.

For reference, the way to check the status of Hyper-V is:

Code: Select all

>dism /online /get-featureinfo /featurename:VirtualMachinePlatform

Deployment Image Servicing and Management tool
Version: 10.0.19041.329

Image Version: 10.0.19041.508

Feature Information:

Feature Name : VirtualMachinePlatform
Display Name : Virtual Machine Platform
Description : Enables platform support for virtual machines
Restart Required : Possible
State : Enabled

Custom Properties:

(No custom properties found)

The operation completed successfully.

Note that it says State : Enabled below the fold.

The fix was to run:

Code: Select all

C:\WINDOWS\system32>dism /online /disable-feature /featurename:VirtualMachinePlatform

... naturally followed by another reboot.

Now VirtualBox is working again. Phew!