FIX: VirtualBox FATAL: INT18: BOOT FAILURE. (Solved)

If you receive the VirtualBox error "FATAL: INT18: BOOT FAILURE" when starting a guest machine with Windows 10/11 OS, continue reading below to fix the problem.

Problem in details. After converting the physical disk of a Windows 10//11 UEFI computer to a Virtual Hard disk (VHD or VHDX) and attaching the VHD/VHDX file to a new VirtualBox machine, the VM couldn't start with fatal error: INT18: BOOT FAILURE or the guest Windows 10 OS couldn't start with error code: 0x0000225.

This tutorial contains detailed instructions to troubleshoot the "INT18: BOOT FAILURE” error in VirtualBox.

How to FIX: INT18 BOOT FAILURE & Windows 10 Error Code 0x0000225 in VirtualBox.

Method 1. Enable I/O APIC & UEFI in VirtualBox.

The fatal error "INT18 BOOT FAILURE" in VirtualBox, commonly appears when you attaching a VHD/VHDX/VMDK file which contains an UEFI operating system. To fix this problem just proceed and enable UEFI on the VirtualBox machine's settings. To do that:

1. Press the X button to close the VM machine window and Power Off the machine.

2. Open the VM Settings and go to System > Motherboard.

3. Here ensure that the Hard Disk is checked and is the first boot device, and at Extended features check the following two (2) options and click OK:

• Enable I/O APIC
• Enable EFI (special OSes only)

4. Try to start the Virtual Machine now. Hopefully it will start without error now.

Method 2. Disable Hyper-V on Host machine.

1. Navigate to Control Panel > Programs and Features > Turn Windows features on or off

2. Uncheck the following features and click OK to apply the change:

• Containers  *
• Hyper-V      *
• Virtual Machine Platform
• Windows Hypervisor Platform
• Windows Sandbox

* Note: The 'Containers' and the 'Hyper-V' features exists only in Windows 10 PRO.

3. Restart the computer after uninstall.

4. Open Command Prompt as Administrator.
5. Type the following command and press Enter:

• bcdedit /set hypervisorlaunchtype off

6. Reboot your PC again.
7. After reboot, start the VirtualBox VM machine and see if the problem is fixed.

Method 3. Fix Boot Problems.

The final method to solve VirtualBox error "FATAL: INT18: BOOT FAILURE" is to fix the boot problems on the Guest machine, by starting the guest machine from a bootable Windows 10 ISO file.*

* Note: If you don't own a Windows 10 ISO file, you can download one directly from Microsoft, by using the Media Creation Tool.

1. Open the Settings of the VirtualBox machine and go to Storage.

2. Click the 1st plus (+) button next to Controller to add optical drive.

3. Click Add and find and open the Windows.iso file.

4. Then select the Windows.iso file and click Choose.

5. After attaching the Windows.iso file in Storage devices…

6. … go to System and drag Optical to the top in order to boot the VM from the attached Windows.iso.

Also, make sure that the "Enable EFI" option is unchecked, otherwise you will not be able to boot from the ISO file. When done, click OK.

7. Start the Virtual Machine and click Next > Repair Your computer.

8. Then select Troubleshoot > Startup Repair.

9. Allow the Startup Repair to run and depending on the result do the following actions:

a. If the Startup Repair can fix the problem, shutdown the virtual machine, set the hard disk as first boot device and try to start again the virtual machine.

b. If the Startup Repair cannot fix the problem, continue to next step.

10. Click Advanced Options and go to Troubleshoot > Command Prompt.

11. In Command prompt give the following commands in order (press enter after each command)

• diskpart
• select disk 0
• list partition

13. Now notice the size of the System partition (e.g. 100MB in this example).

12. Then type the following command and find out the volume number of the System partition by using its size as a reference. *

• list volume

* e.g. As you can see in the screenshot below, in this example, the System partition (100MB) is the volume 2.

13. Now give the following commands to select the system partition (using its volume number), and to assign the drive letter Z: to it. Then exit DISKPART:

• select volume 2    *
• assign letter=Z
• exit

* Note: Change the Volume number "2" according your case.

14. Finally, in command prompt give this command to repair the boot files:

• bcdboot C:\windows /s Z: /f ALL

15. Close all windows, shutdown the virtual machine, set the hard disk as first boot device and start the virtual machine.

That's it! Which method worked for you?
Let me know if this guide has helped you by leaving your comment about your experience. Please like and share this guide to help others.

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