Download and install Windows PE (WinPE) so you can boot from a USB flash drive or an external USB hard drive

Article
03/17/2014

Applies To: Windows 8, Windows 8.1, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2

Boot your PC to a VHD file ("native boot") by using the BCDEdit tool. If you are adding the VHD to a computer that already has a Windows® 8 installation, you will have to add a boot entry to the menu. If you are adding the VHD to a computer that is running an older version of Windows, for example Windows Server® 2008, you will have to update the system partition using the BCDboot tool and then modify the boot menu using the BCDedit tool. The .vhd file format is supported for native boot on a computer that has a Windows® 7 boot environment, but you will have to update the system partition to a Windows 8 environment to use the .vhdx file format.

Copy the .vhd or .vhdx file to the destination computer. For example, at a command prompt, type:
```
copy N:\VHDs\windows.vhdx C:
```
Use the DiskPart tool in Windows PE to attach the VHD on the destination computer. You can attach a VHD by using the Attach vdisk command. This enables the VHD so that it appears on the host as a disk drive instead of as a .vhd file. At a command prompt, type:
```
diskpart
select vdisk file=c:\windows.vhdx
attach vdisk
list volume
select volume <volume_number_of_attached_VHD>
assign letter=v
exit
```
Use the BCDboot tool, located in the \System32 directory of the VHD image or in Windows PE to copy the boot environment files and Boot Configuration Data (BCD) configuration from the \Windows directory in the VHD to the system partition. On a computer that has BIOS firmware, the system partition is the active partition of the first hard disk. For example, to use BCDboot from the VHD image, at a command prompt, type:
```
cd v:\windows\system32
bcdboot v:\windows
```

The BCDboot tool automatically imports information from the existing installation when updating the BCD. The computer is now updated to include a Windows 8 boot environment. You can now follow the steps in the section "To add a native-boot VHD to an existing Windows 8 boot menu" later in this topic.

Copy the .vhd or .vhdx file to the destination computer. For example, at a command prompt, type:
```
copy N:\VHDs\windows.vhdx C:
```
Use the DiskPart tool in Windows PE to attach the VHD on the destination computer. You can attach a VHD by using the Attach vdisk command. This enables the VHD so that it appears on the host as a disk drive instead of as a .vhdx file. At a command prompt, type:
```
diskpart
select vdisk file=C:\windows.vhdx
attach vdisk
list volume
select volume <volume_number_of_attached_VHD>
assign letter=v
exit
```
On a UEFI-based computer, the system partition is hidden by default and must be assigned a drive letter before you run the BCDboot tool. Use the DiskPart tool to locate the EFI system partition and assign a drive letter to it. At a command prompt, type:
```
diskpart
select disk 0
list partition
select partition <x>
assign letter=s
exit
```
Where <x> is the 100 megabyte (MB) EFI system partition that is formatted with FAT.
Use the BCDboot tool, located in the \System32 directory of the VHD image or in Windows PE to copy the boot environment files and BCD configuration from the \Windows directory in the VHD to the system partition. For example, to use BCDboot from the VHD image, at a command prompt, type:
```
cd v:\windows\system32
bcdboot v:\windows
```

The BCDboot tool automatically imports information from the existing installation when updating the BCD. The computer is now updated with a Windows 8 boot environment. You can now follow the steps to add a native-boot VHD to an existing Windows 8 boot menu.

Back up your BCD store using the BCDedit tool with the /export option. For example, at a command prompt, type: bcdedit /export c:\bcdbackup
Copy an existing boot entry for a Windows 8 installation. You will then modify the copy for use as the VHD boot entry. At a command prompt, type:
```
bcdedit /copy {default} /d "vhd boot (locate)"
```
When the BCDedit command is completed successfully, it returns a {GUID} as output in the Command Prompt window.
Locate the {GUID} in the command-prompt output for the previous command. Copy the GUID, including the braces, to use in the following steps.

Set the device and osdevice options for the VHD boot entry. At a command prompt, type:

bcdedit /set {guid} device vhd=[locate]\windows.vhdx
bcdedit /set {guid} osdevice vhd=[locate]\windows.vhdx

Set the boot entry for the VHD as the default boot entry. When the computer restarts, the boot menu will display all of the Windows installations on the computer and boot into the VHD after the operating-system selection countdown is completed. At a command prompt, type:
```
bcdedit /default {guid}
```
Some x86-based systems require a boot configuration option for the kernel in order to detect certain hardware information and successfully native-boot from a VHD. At a command prompt, type:
```
bcdedit /set {guid} detecthal on
```

For more information about how to use the BCDedit tool, see this Microsoft Web site.

Download and install Windows PE (WinPE) so you can boot from a USB flash drive or an external USB hard drive

Update the Boot Menu to Add a VHD

To update a BIOS-based computer to include a Windows 8 boot menu

To update a UEFI-based computer to include a Windows 8 boot menu

To add a native-boot VHD to an existing Windows 8 boot menu

See Also

Tasks

Concepts

Additional resources