BIOS/MBR-based hard drive partitions

Create custom partition layouts for your hard disk drives (HDDs), solid-state drives (SSDs), and other drives when deploying Windows to BIOS–based devices.

Note  If you use a custom partition layout on Windows 10 for desktop editions (Home, Pro, Enterprise, and Education), update the push-button recovery script so the recovery tools can recreate the custom partition layout when needed.

Drive partition rules

When you deploy Windows to a BIOS-based device, you must format hard drives by using an MBR file system. Windows does not support the GUID partition table (GPT) file system on BIOS-based computers.

An MBR drive can have up to four standard partitions. Typically, these standard partitions are designated as primary partitions. For information about how to create additional partitions beyond this limit, see Configure More than Four Partitions on a BIOS/MBR-Based Hard Disk.

Windows partition requirements:

  • System partition

    Each bootable drive must contain a system partition. The system partition must be configured as the active partition.

    The minimum size of this partition is 100 MB.

  • Windows partition

    • This partition must have at least 20 gigabytes (GB) of drive space for 64-bit versions, or 16 GB for 32-bit versions.
    • This partition must be formatted using the NTFS file format.
    • This partition must have enough 10 GB of free space after the user has completed the Out Of Box Experience (OOBE).
    • This partition can have a maximum of 2 terabytes (TB) of space. Software tools to extend the visible partition space beyond 2 TB are not supported on BIOS because they can interfere with software solutions for application compatibility and recovery.
  • Recovery tools partition

    We recommend creating a separate recovery partition to support automatic failover and to support booting Windows BitLocker Drive Encryption-encrypted partitions.

    We recommend that you place this partition in a separate partition, immediately after the Windows partition. This allows Windows to modify and recreate the partition later if future updates require a larger recovery image.

    The Windows Recovery Environment (Windows RE) tools require additional free space:

    • If the partition is less than 500 MB, it must have at least 50 MB of free space.
    • If the partition is 500 MB or larger, it must have at least 320 MB of free space.
    • If the partition is larger than 1 GB, we recommend that it should have at least 1 GB free.

    When calculating free space, note:

    • The recovery image, winre.wim, is typically between 250-300MB, depending on what drivers, languages, and customizations you add.
    • The file system itself can take up additional space. For example, NTFS may reserve 5-15MB or more on a 750MB partition.
  • Data partitions

    The recommended partition layout for Windows 10 does not include utility or data partitions.

    However, if utility or data partitions are required, they should be placed either before the Windows partition or after the Windows RE partition. By keeping the Windows and recovery partitions together, then when future updates of Windows RE area available, Windows will be able to grow the Windows RE partition by shrinking the Windows partition.

    This layout makes it more difficult for end users to remove the data partition and merge the space with the Windows partition. For example, the Windows RE partition may need to be moved to the end of the unused space reclaimed from the data partition, so that the Windows partition can be extended. Windows 10 does not include functionality or utility to facilitate this process. However, manufacturers can develop and provide such a utility if PCs are shipped with data partitions.

    Each partition can have a maximum of 2 terabytes (TB) of space.

    If you're going to be adding more than four total partitions to the disk, see Configure More than Four Partitions on a BIOS/MBR-Based Hard Disk for more info.

Partition layout

If you install Windows using a bootable USB key made by Windows Imaging and Configuration Designer (ICD), it creates the following layout by default: a system partition, a Windows partition, and a recovery tools partition.

diagram of default partition layout: system, windows, and recovery

System and utility partitions

By default, system partitions do not appear in File Explorer. This helps protect end users from accidentally modifying a partition.

To keep system and utility partitions from being reset, we recommend using type 0x27. Do not use any of the following types: 0x7, 0x0c, 0x0b, 0x0e, 0x06, and 0x42.

To set partitions as utility partitions

  1. When you are deploying Windows by using Windows ICD, the partition type will be set automatically.
  2. When you are deploying Windows by using the DiskPart tool, use the set id=27 command after you create the partition.

To verify that system and utility partitions exist

  1. Click Start, right-click This PC, and then click Manage. The Computer Management window opens.
  2. Click Disk Management. The list of available drives and partitions appears.
  3. In the list of drives and partitions, confirm that the system and utility partitions are present and are not assigned a drive letter.

Sample files: configuring disk layout by using Windows PE and DiskPart scripts

For image-based deployment, boot the PC to Windows PE, and then use the DiskPart tool to create the partition structures on your destination PCs.

Note   In these DiskPart examples, the partitions are assigned the letters: System=S, Windows=W, and Recovery=R.

We recommend changing the Windows drive letter to a letter that’s near the end of the alphabet, such as W, to avoid drive letter conflicts. Do not use X, because this drive letter is reserved for Windows PE. After the device reboots, the Windows partition is assigned the letter C, and the other partitions don’t receive drive letters.

If you reboot, Windows PE reassigns disk letters alphabetically, starting with the letter C, without regard to the configuration in Windows Setup. This configuration can change based on the presence of different drives, such as USB flash drives.

The following steps describe how to partition your hard drives and prepare to apply images. You can use the code in the sections that follow to complete these steps.

To partition hard drives and prepare to apply images

  1. Save the following code as a text file (CreatePartitions-BIOS.txt) on a USB flash drive.

    rem == CreatePartitions-BIOS.txt ==
    rem == These commands are used with DiskPart to
    rem    create three partitions
    rem    for a BIOS/MBR-based computer.
    rem    Adjust the partition sizes to fill the drive
    rem    as necessary. ==
    select disk 0
    rem == 1. System partition ======================
    create partition primary size=100
    format quick fs=ntfs label="System"
    assign letter="S"
    rem == 2. Windows partition =====================
    rem ==    a. Create the Windows partition =======
    create partition primary
    rem ==    b. Create space for the recovery tools  
    shrink minimum=500
    rem       ** Update this size to match the size of
    rem          the recovery tools (winre.wim)
    rem          plus some free space.
    rem ==    c. Prepare the Windows partition ====== 
    format quick fs=ntfs label="Windows"
    assign letter="W"
    rem == 3. Recovery tools partition ==============
    create partition primary
    format quick fs=ntfs label="Recovery"
    assign letter="R"
    set id=27
    list volume
  2. Use Windows PE to boot the destination computer.

  3. Clean and partition the drive. In this example, F is the letter of the USB flash drive.

    DiskPart /s F:\CreatePartitions-BIOS.txt
  4. If you use a custom partition layout on Windows 10 for desktop editions, update the push-button recovery script so the recovery tools can recreate the custom partition layout when needed.

Next steps

Use a deployment script to apply the Windows images on the newly created partitions. For more information, see Capture and Apply Windows, System, and Recovery Partitions.

Configure More than Four Partitions on a BIOS/MBR-Based Hard Disk

Configure UEFI/GPT-Based Hard Drive Partitions

BitLocker Drive Encryption

Configuring Disk Mirroring