Understanding the Root Cause
The error message "VT-x/AMD-V hardware acceleration is not available on your system" indicates that VirtualBox cannot access the CPU's virtualization extensions. These extensions are required for the VM to run efficiently. On modern Windows systems, especially Windows 11, this issue is rarely due to a missing BIOS setting alone. Instead, it is typically caused by other hypervisors taking exclusive control of these resources.
Windows 11 introduces several security features that rely on hardware virtualization, such as Virtualization-Based Security (VBS) and Hypervisor-Enforced Code Integrity. When these are active, they lock the VT-x feature for their own use, leaving VirtualBox unable to access it. Additionally, if you have previously installed Windows Subsystem for Linux (WSL2) or Docker Desktop, they may have enabled the "Hyper-V Platform" or "Virtual Machine Platform" Windows services, which conflict with VirtualBox.
Enabling Virtualization in BIOS/UEFI
The first step is to ensure that your processor's virtualization technology is actually turned on at the hardware level. If this is disabled, no software configuration will help. Restart your computer and enter the BIOS or UEFI setup menu. This is usually done by pressing F2, F10, Delete, or Esc during the initial boot sequence, depending on your manufacturer.
- Locate the Setting: Look for a tab labeled "Advanced," "CPU Configuration," or "Security." The exact name varies by motherboard maker.
- Enable VT-x/AMD-V: Find the option named "Intel Virtualization Technology," "VT-x," "SVM Mode," or "AMD-V." Set it to Enabled.
- Save and Exit: Save your changes (usually
F10) and reboot into Windows.
If you are unsure whether this setting was already enabled, proceed to the next section to check Windows-level conflicts, as disabling Windows hypervisors often resolves the issue even if BIOS is correct.
Disabling Conflicting Windows Features
Windows 11 uses a type-1 hypervisor architecture for certain security and development features. You need to disable these to free up VT-x for VirtualBox. Open the Start menu, type Turn Windows features on or off, and select the result from the Control Panel.
In the list that appears, uncheck the following options if they are currently checked:
- Hyper-V
- Virtual Machine Platform
- Windows Hypervisor Platform
- Windows Subsystem for Linux
- Windows Sandbox
Click OK and allow Windows to apply the changes. You will be prompted to restart your computer. After rebooting, try launching your Kubuntu VM again. In many cases, simply turning off the "Virtual Machine Platform" is sufficient to restore VT-x availability.
Disabling Core Isolation and Memory Integrity
If the above steps do not work, you must address Virtualization-Based Security (VBS). This is a deeper layer of protection that runs on top of the hypervisor. Navigate to Settings > Privacy & security > Device security. Under the "Core isolation" section, click Core isolation details. Turn off the toggle for Memory integrity. This feature often blocks third-party hypervisors from accessing low-level memory addresses required for VT-x.
Using Command Line Diagnostics
Sometimes the GUI settings do not reflect the true state of the hypervisor. You can verify which component is blocking VT-x using PowerShell. Open PowerShell as Administrator and run the following command:
bcdedit /enum | findstr hypervisorIf the output shows hypervisorlaunchtype Auto, it means a hypervisor is starting at boot. To disable it completely, run:
bcdedit /set hypervisorlaunchtype offRestart your machine after running this command. This forces Windows to stop loading its internal hypervisor, allowing VirtualBox to take full control of the CPU's virtualization capabilities. Note that this may impact WSL2 functionality, so you might need to re-enable it later if you use Linux containers.
Alternative: Using WSL2 or Hyper-V Directly
If you require deep integration with Windows security features and cannot disable them, consider switching your virtualization strategy. VirtualBox is not designed to coexist with Windows Hyper-V. For running Linux distributions like Kubuntu, you might find better performance and compatibility using WSL2 directly within Windows. Alternatively, if you need full graphical desktop environments, Microsoft offers Hyper-V Manager which supports Ubuntu natively through the Microsoft Store.
For users who still prefer VirtualBox but need network isolation similar to VPN tunneling, you can configure bridged networking. See how to Configure Two Virtual Machines: Host VirtualBox to Use Guest's VPN for advanced networking setups that bypass some hypervisor limitations.
Frequently Asked Questions
Why does VT-x show as available in Task Manager but VirtualBox still fails?
This happens because Task Manager only checks if the CPU supports virtualization, not if it is accessible to your application. VirtualBox requires exclusive access to the VT-x instruction set, which is blocked if another hypervisor like Hyper-V or VBS is active. Disabling those Windows features resolves the discrepancy.
Can I use VirtualBox and WSL2 at the same time?
No, they cannot run simultaneously because both require the same underlying hardware virtualization resources. You must choose one: either keep WSL2 enabled and use Hyper-V based tools, or disable WSL2 and Virtual Machine Platform to use VirtualBox. Switching between them requires a full system reboot.
Does disabling Memory Integrity affect gaming performance?
Disabling Memory Integrity has a negligible impact on gaming performance. However, it reduces the security posture of your Windows installation against certain kernel-level exploits. If security is a priority, consider using Hyper-V instead of VirtualBox, as it is fully supported by Windows 11.
What should I do if my BIOS does not have an VT-x option?
If the option is missing, your CPU may not support virtualization, which is rare for processors made after 2005. Ensure you are looking in the correct sub-menu, as it is sometimes hidden under "Overclocking" or "Advanced CPU Configuration." If it is truly absent, you cannot run VirtualBox VMs.
How do I revert changes if I break my Windows boot?
If you modified the BCD store and Windows fails to boot, you can use the Windows Recovery Environment. Select "Troubleshoot" > "Advanced options" > "Command Prompt" and run bcdedit /set hypervisorlaunchtype auto to restore the default behavior. Always create a system restore point before making deep registry or boot changes.