Convert an MBR disk into a GPT disk

Applies To: Windows 10, Windows 8.1, Windows Server (Semi-Annual Channel), Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012

Master Boot Record (MBR) disks use the standard BIOS partition table. GUID Partition Table (GPT) disks use Unified Extensible Firmware Interface (UEFI). One advantage of GPT disks is that you can have more than four partitions on each disk. GPT is also required for disks larger than two terabytes (TB).

You can change a disk from MBR to GPT partition style as long as the disk contains no partitions or volumes.

Before you convert a disk, backup any data on it and close any programs that are accessing the disk.

You must be a member of the Backup Operators or Administrators group, at minimum, to complete these steps.

Converting using the Windows interface

Back up or move the data on the basic MBR disk you want to convert into a GPT disk.

If the disk contains any partitions or volumes, right-click each and then click Delete Partition or Delete Volume.

Right-click the MBR disk that you want to change into a GPT disk, and then click Convert to GPT Disk.

Converting using a command line

Use the following steps to convert an empty MBR disk to a GPT disk. There’s also a MBR2GPT.EXE tool that you can use, but it’s a little complicated — see Convert MBR partition to GPT for more details.

Back up or move the data on the basic MBR disk you want to convert into a GPT disk.

Open an elevated command prompt by right-clicking Command Prompt and then choosing Run as Administrator.

Type diskpart . If the disk does not contain any partitions or volumes, skip to step 6.

At the DISKPART prompt, type list disk . Note the disk number you want to convert.

At the DISKPART prompt, type select disk .

At the DISKPART prompt, type clean .

Running the clean command will delete all partitions or volumes on the disk.

At the DISKPART prompt, type convert gpt .

Changing the Friendly Name of a Boot Entry

In Windows, the items that appear in the Windows Boot Manager are the descriptions of each boot entry.

Typically, after you copy a boot entry, you change the friendly name of the newly created entry to distinguish it from the original.

You can also change the friendly name to make it easier to recognize customized boot entries. A string that precisely describes the entry can save significant time and effort.

For example, the following friendly name strings add little value.

However, more precise strings, such as the ones that follow, make the boot choice much easier.

NoteВ В When a boot entry is configured for debugging (/debug /debugport) or for Emergency Management Services (EMS) (/redirect) on an x86- or an x64-based system, the boot loader appends a bracketed phrase ([debugger enabled] or [ems enabled]) to the friendly name that appears in the boot menu. However, the boot loader omits the bracketed phrase from the boot menu when the friendly name and the bracketed phrase together exceed 70 characters. To restore the bracketed phrase, shorten the friendly name.

To change the friendly name of a boot entry in a Boot.ini file, you can use Bootcfg or edit the Boot.ini file in Notepad. On systems that store boot options in EFI NVRAM, use Bootcfg.

To change the friendly name of a boot entry for Windows, use BCDEdit.

Administrative privileges are required to update the boot configuration. Changing some boot entry options could render your computer inoperable.

Using BCDEdit

To change the description of a boot entry as it appears on the boot menu, you can use the /set IDdescription option. The command uses the following syntax. The ID is the GUID that is associated with the boot entry (or one of the well-known identifiers, for example, ).

If you are using Windows PowerShell, you must use quotes around the boot entry identifier, for example: «<49916baf-0e08-11db-9af4-000bdbd316a0>« or ««.

To change the description of the boot entry that corresponds to the operating system that is currently running, use the following example:

You can also change the description when you copy an existing boot entry using the /d option.

Using Bootcfg

With Bootcfg, you can change the friendly name of a boot entry only while copying the entry. Use the Bootcfg /copy switch to copy the entry and change its friendly name.

The following Bootcfg command copies the first boot entry to create a new entry. The /ID switch specifies the line number of the entry being copied. The /d (description) switch specifies the friendly name of the newly-created entry.

For complete instructions for using Bootcfg, see Help and Support Services. For examples, see Using Boot Parameters.

Editing the Boot.ini File

In the Boot.ini file, the friendly name of a boot entry appears in the boot entry in quotation marks.

For example, the following sample from a Boot.ini file has duplicate boot entries for Microsoft Windows 10 Professional.

To change the friendly name of a boot entry, type over the quoted string in the boot entry. In the following example, because the first entry will be customized for debugging, the name is changed to Windows 10 Debug.

BCDBoot Command-Line Options

BCDBoot is a command-line tool used to configure the boot files on a PC or device to run the Windows operating system. You can use the tool in the following scenarios:

• Add boot files to a PC after applying a new Windows image. In a typical image-based Windows deployment, use BCDBoot to set up the firmware and system partition to boot to your image. To learn more, see Capture and Apply Windows, System, and Recovery Partitions.
• Set up the PC to boot to a virtual hard disk (VHD) file that includes a Windows image. To learn more, see Boot to VHD (Native Boot): Add a Virtual Hard Disk to the Boot Menu.
• Repair the system partition. If the system partition has been corrupted, you can use BCDBoot to recreate the system partition files by using new copies of these files from the Windows partition.
• Set up or repair the boot menu on a dual-boot PC. If you’ve installed more than one copy of Windows on a PC, you can use BCDBoot to add or repair the boot menu.

File Locations

In Windows and Windows Preinstallation Environment (WinPE)

In the Windows Assessment and Deployment Kit (WindowsВ ADK):

C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Deployment Tools\amd64\BCDBoot\BCDBoot.exe

Supported operating systems

BCDBoot can copy boot environment files from images of WindowsВ 10, Windows 8.1, WindowsВ 8, WindowsВ 7, WindowsВ Vista, Windows ServerВ 2016 Technical Preview, WindowsВ Server 2012 R2, Windows ServerВ 2012, Windows ServerВ 2008В R2, or WindowsВ ServerВ 2008.

How It Works

To configure the system partition, BCDBoot copies a small set of boot-environment files from the installed Windows image to the system partition.

BCDBoot can create a Boot Configuration Data (BCD) store on the system partition using the latest version of the Windows files:

• BCDBoot creates a new BCD store and initialize the BCD boot-environment files on the system partition, including the Windows Boot Manager, using the %WINDIR%\System32\Config\BCD-Template file.
• New in WindowsВ 10: During an upgrade, BCDBoot preserves any other existing boot entries, such as debugsettings, when creating the new store. Use the /c option to ignore the old settings and start fresh with a new BCD store.
• If there is already a boot entry for this Windows partition, by default, BCDBoot erases the old boot entry and its values. Use the /m option to retain the values from an existing boot entry when you update the system files.
• By default, BCDBoot moves the boot entry for the selected Windows partition to the top of the Windows Boot Manager boot order. Use the /d option to preserve the existing boot order.

On UEFI PCs, BCDBoot can update the firmware entries in the device’s NVRAM:

• BCDBoot adds a firmware entry in the NVRAM to point to the Windows Boot Manager. By default, this entry is placed as the first item in the boot list. Use the /p option to preserve the existing UEFI boot order. Use /addlast to add it to the bottom of the boot order list.

Command-Line Options

The following command-line options are available for BCDBoot.exe.

BCDBOOT [/l ] [/s [/f ]] [/v] [/m [<OS Loader GUID>]] [/addlast or /p] [/d] [/c]

Required. Specifies the location of the Windows directory to use as the source for copying boot-environment files.

The following example initializes the system partition by using BCD files from the C:\Windows folder:

Optional. Specifies the locale. The default is US English ( en-us ).

The following example sets the default BCD locale to Japanese:

Optional. Specifies the volume letter of the system partition. This option should not be used in typical deployment scenarios.

Use this setting to specify a system partition when you are configuring a drive that will be booted on another computer, such as a USB flash drive or a secondary hard drive.

UEFI:

BCDBoot copies the boot files to either the EFI system partition, or the partition specified by the /s option.

BCDBoot creates the BCD store in the same partition.

By default, BCDBoot creates a Windows Boot Manager entry in the NVRAM on the firmware to identify the boot files on the system partition. If the /s option is used, then this entry is not created. Instead, BCDBoot relies on the default firmware settings to identify the boot files on the system partition. By the UEFI 2.3.1 spec, the default firmware settings should open the file: \efi\boot\bootx64.efi in the EFI System Partition (ESP).

BIOS:

BCDBoot copies the boot files to either the active partition on the primary hard drive, or the partition specified by the /s option.

BCDBoot creates the BCD store in the same partition.

The following example copies BCD files from the C:\Windows folder to a system partition on a secondary hard drive that will be booted on another computer. The system partition on the secondary drive was assigned the volume letter S:

The following example creates boot entries on a USB flash drive with the volume letter S, including boot files to support either a UEFI-based or a BIOS-based computer:

Optional. Specifies the firmware type. Valid values include UEFI , BIOS , and ALL .

On BIOS/MBR-based systems, the default value is BIOS . This option creates the \Boot directory on the system partition and copies all required boot-environment files to this directory.

On UEFI/GPT-based systems, the default value is UEFI . This option creates the \Efi\Microsoft\Boot directory and copies all required boot-environment files to this directory.

When you specify the ALL value, BCDBoot creates both the \Boot and the \Efi\Microsoft\Boot directories, and copies all required boot-environment files for BIOS and UEFI to these directories.

If you specify the /f option, you must also specify the /s option to identify the volume letter of the system partition.

The following example copies BCD files that support booting on either a UEFI-based or a BIOS-based computer from the C:\Windows folder to a USB flash drive that was assigned the volume letter S:

Optional. Enables verbose mode. Example:

Optional. Merges the values from an existing boot entry into a new boot entry.

By default, this option merges only global objects. If you specify an OS Loader GUID, this option merges the loader object in the system template to produce a bootable entry.

The following example merges the operating-system loader in the current BCD store that the specified GUID identifies in the new BCD store:

Optional. Specifies that the Windows Boot Manager firmware entry should be added last. The default behavior is to add it first. Cannot be used with /p.

Optional. Specifies that the existing Windows Boot Manager firmware entry position should be preserved in the UEFI boot order. If entry does not exist, a new entry is added in the first position. Cannot be used with /addlast.

By default, during an upgrade BCDBoot moves the Windows Boot Manager to be the first entry in the UEFI boot order.

Optional. Preserves the existing default operating system entry in the object in Windows Boot Manager.

Optional. Specifies that any existing BCD elements should not be migrated.

New for WindowsВ 10: By default, during an upgrade, BCD elements such as debugsettings or flightsigning are preserved.

Repair the system partition

If the system partition has been corrupted, you can use BCDBoot to recreate the system partition files by using new copies of these files from the Windows partition.

Boot your PC to a command line. For example, boot to the Windows installation disk and press Shift+F10, or boot to Windows PE (WinPE: Create USB Bootable drive).

Use Diskpart to determine which drive letter contains your Windows partition and system partition ( diskpart, list vol, exit ).

Optional: Format your system partition: format (drive letter of your system partition) /q

Add a boot entry for your Windows partition: bcdboot D:\Windows

Reboot the PC. Windows should appear.

Set up or repair the boot menu on a dual-boot PC

When setting up a PC to boot more than one operating system, you may sometimes lose the ability to boot into one of the operating systems. The BCDBoot option allows you to quickly add boot options for a Windows-based operating system. To set up a dual-boot PC:

Install a separate hard drive or prepare a separate partition for each operating system.

Install the operating systems. For example, if your PC has WindowsВ 7, install WindowsВ 10 onto the other hard drive or partition.

Reboot the PC. The boot menus should appear with both operating systems listed.

If both operating systems aren’t listed:

Open a command line, either as an administrator from inside Windows, or by booting to a command line using the Windows installation media and pressing Shift+F10, or by booting to Windows PE (WinPE: Create USB Bootable drive).

Add boot options for a Windows operating system.

Reboot the PC. Now, the boot menu will show both menu options.

Troubleshooting

For information about repairing the boot files on a PC with Windows XP and a more recent version of Windows such as WindowsВ 7, see the Microsoft Knowledge Base Article 2277998.

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