Fix: VirtualBox 64-Bit Guest Option Greyed Out

You've got a 64-bit host, plenty of RAM, and you're trying to create a new 64-bit Linux or Windows VM in VirtualBox. But when you pick the OS version in the dropdown, everything says 32-bit. No 64-bit option at all. Drives you nuts. This happens almost always after a Windows 10/11 feature update, or on a brand new machine.

The culprit here is almost always one of three things: virtualization is disabled in BIOS/UEFI, Hyper-V is running on your Windows host, or Windows Defender Device Guard / Credential Guard is blocking the hypervisor layer. VirtualBox needs hardware virtualization (VT-x or AMD-V) to run 64-bit guests. If the host OS has already grabbed that hardware, VirtualBox can't use it. Simple as that.

What You're Seeing

Open VirtualBox, click New, name your VM, and in the Type dropdown you see "Microsoft Windows" but the Version list shows only "Windows 10 (32-bit)" or "Windows 7 (32-bit)". No 64-bit entries. Same for Linux or any other OS. The VM creation wizard doesn't lie — if it ain't there, VirtualBox can't use hardware virtualization.

Fix It: Step by Step

Check BIOS/UEFI virtualization setting. Reboot your machine and enter BIOS (usually F2, Del, or F10 during boot). Look for "Intel Virtualization Technology", "VT-x", "AMD-V", or "SVM Mode". Enable it. Save and exit. This is the single most common fix. I've seen Dell, HP, and Lenovo systems ship with this disabled by default.
Check if Hyper-V is enabled on Windows. Open PowerShell as admin and run Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V. If the state is "Enabled", you need to disable it. Run Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V and reboot. Hyper-V hogs the VT-x layer. VirtualBox can't share it.
Disable Windows features that use virtualization. Go to Control Panel > Programs and Features > Turn Windows features on or off. Uncheck these if they're checked: Hyper-V, Windows Sandbox, Windows Subsystem for Linux (WSL2 in some cases), and Virtual Machine Platform. Reboot after changes.
Kill Device Guard and Credential Guard. These are enabled via Group Policy or registry. Open PowerShell as admin and run Get-CimInstance -Namespace root\Microsoft\Windows\DeviceGuard -ClassName Win32_DeviceGuard. If "VirtualizationBasedSecurityStatus" is 2, you need to disable them. Run Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-DeviceGuard (if available), or use Group Policy Editor: Computer Configuration > Administrative Templates > System > Device Guard > Turn on Virtualization Based Security — set to Disabled. Reboot.
Verify the fix. Open Task Manager on Windows, go to Performance tab. Under CPU, look for "Virtualization: Enabled". If it says Enabled and you still don't see 64-bit options in VirtualBox, you missed something in step 2 or 3.

If It Still Fails

You've done the steps above, rebooted twice, and still nothing. Here's what else can trip you up:

Windows 11 strict requirements. Microsoft forces Virtualization Based Security (VBS) on some new Win11 installs. Even if you disable Hyper-V in features, VBS can still be active. Run msinfo32 and check "Virtualization-based security" line. If it says Running, you need to dig into group policy or use the Disable-VBS script from Microsoft's docs.
Third-party antivirus. Some security suites (looking at you, old Symantec and McAfee versions) hook into the hypervisor layer. Uninstall them temporarily to test. Reinstall a lightweight AV if needed.
VMware Workstation or other hypervisors. If you have VMware Player or Workstation installed, it might grab VT-x. Uninstall it, reboot, test VirtualBox. You can reinstall later — they don't play nice together.
Old BIOS version. Some motherboards had buggy ACPI tables that misreport virtualization capability. Update your BIOS to the latest. I've fixed this exact issue on a Dell XPS 15 by going from BIOS 1.3 to 1.7.
Physical hardware limitation. Rare but real — very old CPUs (pre-2008) genuinely don't have VT-x. Check your CPU specs on Intel ARK or AMD's site. If it doesn't support virtualization, you're out of luck for 64-bit guests in VirtualBox. Use QEMU with software emulation instead.

Quick Test Script

Run this in PowerShell to see what's blocking VT-x:

# Check if Hyper-V is installed
Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V

# Check Device Guard status
Get-CimInstance -Namespace root\Microsoft\Windows\DeviceGuard -ClassName Win32_DeviceGuard

# Check Virtualization Based Security
Get-CimInstance -ClassName Win32_ComputerSystem | Select-Object -Property VirtualizationFirmwareEnabled

If VirtualizationFirmwareEnabled returns True but VirtualBox still won't show 64-bit guests, you've got a software conflict. Disable everything I listed above and reboot clean.

One last thing: never bother reinstalling VirtualBox for this issue. It's not a corrupt install problem. The 64-bit option missing is always a hardware or host OS permission problem. Save yourself the download time.