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Change a GUID Partition Table Disk into a Master Boot Record Disk

  • Article

Applies To: Windows Server 2008, Windows Vista

Master boot record (MBR) disks use the standard BIOS partition table. GUID partition table (GPT) disks use extensible firmware interface (EFI). MBR disks do not support more than four partitions on each disk. The MBR partition method is not recommended for disks larger than 2 terabytes.

You can change a disk from GPT to MBR partition style as long as the disk is empty and contains no volumes.

Backup Operators or Administrator is the minimum membership required.

Note

Before you convert disks, close any programs that are running on those disks.

Changing a GUID partition table disk into a master boot record disk

  • Using the Windows interface

  • Using a command line

To change a GUID partition table disk into a master boot record disk using the Windows interface

  1. Back up or move all volumes on the basic GUID partition table (GPT) disk you want to convert into a master boot record (MBR) disk.

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

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

To change a GUID partition table disk into a master boot record disk using command line

  1. Back up or move all volumes on the basic GUID partition table (GPT) disk you want to convert into a master boot record (MBR) disk.

  2. Open a command prompt and type diskpart. If the disk does not contain any partitions or volumes, skip to step 6.

  3. At the DISKPART prompt, type list volume. Make note of the volume number you want to delete.

  4. At the DISKPART prompt, type select volume <volumenumber>.

  5. At the DISKPART prompt, type delete volume.

  6. At the DISKPART prompt, type list disk. Make note of the disk number of the disk that you want to convert to a GPT disk.

  7. At the DISKPART prompt, type select disk <disknumber>.

  8. At the DISKPART prompt, type convert mbr.

Important

The disk must be empty to convert it to an MBR disk. Back up your data and then delete all partitions or volumes before converting the disk.

Value Description

list volume

Displays a list of basic and dynamic volumes on all disks.

select volume

Selects the specified volume, where volumenumber is the volume number, and gives it focus. If no volume is specified, the select command lists the current volume with focus. You can specify the volume by number, drive letter, or mount point path. On a basic disk, selecting a volume also gives the corresponding partition focus.

delete volume

Deletes the selected volume. You cannot delete the system volume, boot volume, or any volume that contains the active paging file or crash dump (memory dump).

list disk

Displays a list of disks and information about them, such as their size, amount of available free space, whether the disk is a basic or dynamic disk, and whether the disk uses the master boot record (MBR) or GUID partition table (GPT) partition style. The disk marked with an asterisk (*) has focus.

select disk

Selects the specified disk, where disknumber is the disk number, and gives it focus.

convert mbr

Converts an empty basic disk with the GUID Partition Table (GPT) partition style to a basic disk with the master boot record (MBR) partition style.

Additional references