VirtualBox: VERR_VMX_MSR_VMXON_DISABLED

Question

Yesterday I created my first VirtualBox VM (v4.3.28)! I learned that in order to run a 64-bit OS (in my case, Windows 7), I needed to enable Virtual Technology (VT) in my BIOS/UEFI (Intel i7-3770K). I set up my VM to snapshot, and it continued to turn on until after rebooting my physical computer. Now I receive the following error and no longer see 64-bit OS options:

Failed to open a session for the virtual machine <Name of VM>.

VT-x is disabled in the BIOS. (VERR_VMX_MSR_VMXON_DISABLED).

Result Code: E_FAIL (0x80004005)
Component: Console
Interface: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}

I found several posts about this, however the solutions have been to (1) Enable VT via BIOS (as it still is) and (2) Enable a VirtualBox option under Settings>System>Acceleration. Regarding the latter, I am now unable to access the Acceleration tab (the tab is gray). I am not sure how to proceed. Any discussion is greatly appreciated! Thank you.

Answer 1

Acceleration tab is greyed out because the VM is not powered off. you cannot change such settings if it is in a saved state.

If you still have your snapshot, I would strongly recommend removing it and configuring the VM afterwards. Else, you'll loose the configuration if you restore it.

If this still doesn't work, couple of things to check:

• Make sure you enable VT-x and not some other VT. VT-d exists also per exemple, but is not what you need.
• After enabling VT-x, do a full power off. VT-x is not enabled on a simple reboot or BIOS settings save.
• Double check for Hyper-V or VMware at startup - they will lock VT-x and VirtualBox will not be able to use it.

Answer 2

Below post may be helpful: https://superuser.com/questions/22915/how-do-i-enable-vt-x

For me (Intel i5 vPro), below two steps helped resolve this issue: 1. Enable in host computer's BIOS the option "Virtualization"; which i enabled and "Save & Quit", and rebooted. 2. Then on VBox additions "Setting -> System -> Acceleration(tab)" enable "Enable VT-x/AMD-V". 3. Start the VBox addition; it should hopefully resolve the issue.

It helped me solve the above issue.