VirtualBox Guest VM cannot start on Win10

Problem: Virtualbox Guest VM (Linux OS in my case) cannot start on Windows 10 with the error: “ VT-x is not Available”.

If you have tried the following:

• Enable VT-x in BIOS
• Disable Hyper-V on Windows 10
• Play around any kind of settings in local Group Policy

But, the problem still persists. It could be due to Windows Defender Credential Guard. This setting cannot be disabled via UI.

Microsoft provides a WIKI on how to do so: https://docs.microsoft.com/en-us/windows/security/identity-protection/credential-guard/credential-guard-manage

But this WIKI is really long and confusing. Actually, what you need to do is:

1. Save this powershell scripts in to a file: https://docs.microsoft.com/en-us/windows/security/identity-protection/credential-guard/dg-readiness-tool . For instance, ‘DG_Readiness_Tool_v3.6.ps1’
2. Launch a Windows Power Shell as Administrator, cd to the directory where you save the scripts
3. Power off your VirtualBox Guest VM
4. Run this scripts: ./DG_Readiness_Tool_v3.6.ps1 -Disable -AutoReboot
5. The Windows 10 will be rebooted automatically, then two screens will pop up during the rebooting to ask your confirmation to disable Defender Guard
6. After the Windows 10 is up and running, boot up the Guest VM. Good luck