Windows Setup: Installing using the MBR or GPT partition style

When installing Windows on UEFI-based PCs using Windows Setup, your hard drive partition style must be set up to support either UEFI mode or legacy BIOS-compatibility mode.

For example, if you receive the error message: “Windows cannot be installed to this disk. The selected disk is not of the GPT partition style”, it’s because your PC is booted in UEFI mode, but your hard drive is not configured for UEFI mode. You’ve got a few options:

Reboot the PC in legacy BIOS-compatibility mode. This option lets you keep the existing partition style. For more info, see Boot to UEFI Mode or Legacy BIOS mode.

Configure your drive for UEFI by using the GPT partition style. This option lets you use the PC’s UEFI firmware features.

You can preserve your data and convert the drive using the MBR2GPT tool. You can also choose to reformat the drive using the instructions below. Reformatting will erase all the data on the drive.

Why should I convert my drive?

Many PCs now include the ability to use the UEFI version of BIOS, which can speed up boot and shutdown times and can provide additional security advantages. To boot your PC in UEFI mode, you’ll need to use a drive formatted using the GPT drive format.

Many PCs are ready to use UEFI, but include a compatibility support module (CSM) that is set up to use the legacy version of BIOS. This version of BIOS was developed in the 1970s and provides compatibility to a variety of older equipment and network configurations, and requires a drive that uses the MBR drive format.

However, the basic MBR drive format does not support drives over 4TB. It’s also difficult to set up more than four partitions. The GPT drive format lets you set up drives that are larger than 4 terabytes (TB), and lets you easily set up as many partitions as you need.

Reformatting the drive using a different partition style

To wipe and convert the drive by using Windows Setup

Turn off the PC, and put in the Windows installation DVD or USB key.

Boot the PC to the DVD or USB key in UEFI mode. For more info, see Boot to UEFI Mode or Legacy BIOS mode.

When choosing an installation type, select Custom.

On the Where do you want to install Windows? screen, select each of the partitions on the drive, and select Delete. The drive will show a single area of unallocated space.

Select the unallocated space and click Next. Windows detects that the PC was booted into UEFI mode, and reformats the drive using the GPT drive format, and begins the installation.

To manually wipe a drive and convert it to GPT:

Turn off the PC, and put in the Windows installation DVD or USB key.

Boot the PC to the DVD or USB key in UEFI mode. For more info, see Boot to UEFI Mode or Legacy BIOS mode.

From inside Windows Setup, press Shift+F10 to open a command prompt window.

Open the diskpart tool:

Identify the drive to reformat:

Select the drive, and reformat it:

Close the command prompt window.

Continue the Windows Setup installation.

When choosing an installation type, select Custom. The drive will appear as a single area of unallocated space.

Select the unallocated space and click Next. Windows begins the installation.

Make sure Windows Setup boots to the correct firmware mode

To automate this process, you’ll need to run Windows Setup through Windows PE, and use a script to detect which mode you’re in before installing Windows. For more info, see WinPE: Boot in UEFI or legacy BIOS mode.

UEFI/GPT-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 Unified Extensible Firmware Interface (UEFI)–based devices.

If you use a custom partition layout on WindowsВ 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.

Partition Requirements

When you deploy Windows to a UEFI-based device, you must format the hard drive that includes the Windows partition by using a GUID partition table (GPT) file system. Additional drives may use either the GPT or the master boot record (MBR) file format.

A GPT drive may have up to 128 partitions.

Each partition can have a maximum of 18 exabytes (

18.8 million terabytes) of space.

System partition

The device must contain a system partition. On GPT drives, this is known as the EFI System Partition, or the ESP. This partition is usually stored on the primary hard drive. The device boots to this partition.

The minimum size of this partition is 100 MB, and must be formatted using the FAT32 file format.

This partition is managed by the operating system, and should not contain any other files, including Windows RE tools.

For Advanced Format 4K Native drives (4-KB-per-sector) drives, the minimum size is 260 MB, due to a limitation of the FAT32 file format. The minimum partition size of FAT32 drives is calculated as sector size (4KB) x 65527 = 256 MB.

Advanced Format 512e drives are not affected by this limitation, because their emulated sector size is 512 bytes. 512 bytes x 65527 = 32 MB, which is less than the 100 MB minimum size for this partition.

Microsoft reserved partition (MSR)

In WindowsВ 10, the size of the MSR is 16 MB.

Add an MSR to each GPT drive to help with partition management. The MSR is a reserved partition that does not receive a partition ID. It cannot store user data.

Other utility partitions

Any other utility partitions not managed by Windows must be located before the Windows, data, and recovery image partitions. This allows end users to perform actions such as resizing the Windows partition without affecting system utilities.

Protect end users from accidentally modifying utility partitions by identifying them using a GPT attribute. This prevents these partitions from appearing in File Explorer.

To set partitions as utility partitions

• When you’re deploying Windows by using DiskPart, use the attributes volume set GPT_ATTRIBUTE_PLATFORM_REQUIRED command after you create the partition to identify the partition as a utility partition. For more information, see the MSDN topic: PARTITION_INFORMATION_GPT structure.

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.

Windows partition

• The partition must have at least 20 gigabytes (GB) of drive space for 64-bit versions, or 16 GB for 32-bit versions.
• The Windows partition must be formatted using the NTFS file format.
• The Windows partition must have 16 GB of free space after the user has completed the Out Of Box Experience (OOBE) and Automatic Maintenance has completed.

Recovery tools partition

This partition must be at least 300 MB.

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

• A minimum of 52 MB is required but 250 MB is recommended, to accomodate future updates, especially with custom partition layouts.

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.

This partition must use the Type ID: DE94BBA4-06D1-4D40-A16A-BFD50179D6AC.

The recovery tools should be in a separate partition than the Windows partition to support automatic failover and to support booting partitions encrypted with WindowsВ BitLocker Drive Encryption.

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

Data partitions

The recommended partition layout for WindowsВ 10 does not include data partitions. However, if data partitions are required, they should be placed after the Windows RE partition. This allows future updates to Windows RE 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. To do so, the Windows RE partition must be moved to the end of the unused space reclaimed from the data partition, so that the Windows partition can be extended.

WindowsВ 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.

Partition layout

The default partition layout for UEFI-based PCs is: a system partition, an MSR, a Windows partition, and a recovery tools partition.

This layout lets you use WindowsВ BitLocker Drive Encryption through both Windows and through the Windows Recovery Environment.

Sample files: configure drive partitions by using WindowsВ 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.

In these DiskPart examples, the partitions are assigned the letters: System=S, Windows=W, and Recovery=R. The MSR partition does not receive a drive letter.

Change 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, WindowsВ 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

Copy and save the CreatePartitions-UEFI.txt file to a USB flash drive.

Use WindowsВ PE to boot the destination PC.

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

1. If you use a custom partition layout on WindowsВ 10 for desktop editions, update the push-button recovery script so the recovery tools can recreate the custom partition layout when needed.

To avoid bare metal recovery boot issues due to partition size, manufacturers should allow the bare metal recovery feature’s auto generation script to create the partition used for the recovery WIM. If manufacturer’s want to use a custom DISKPART script to create partitions, the recommended minimum partition size is 990MB with a minimum of 250MB of free space.

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.

Create Hard Disk Partitions Before Installing Windows 10/8/7

Learn how to create hard disk partitions before installing Windows 10/8/7 operating system on your hard drive for your system, applications, games and other data better organized.

By AOMEI / Last Updated January 16, 2020

Why create partition before installing Windows 10/8/7?

By default, Windows will generate a system reserved partition (on MBR disk) or recovery partition (on GPT disk) and C: drive if you select an unallocated space to install Windows operating system (OS). Since GPT disks can have multiple primary partitions as you like, it is no big deal to have one or more extra small partitions on a GPT disk, but things will be different for MBR disks, because you can have at most 4 primary partitions on a MBR disk.

If your computer supports UEFI boot mode, you can convert MBR to GPT disk without data loss. Otherwise, for those people who want to install multiple OS on one MBR drive, the 4 primary partitions are really precious. Besides, you can only have three primary partitions if you have logical partition(s) on the same disk. Therefore, to make full use of the primary partitions is to allow Windows to be installed into one partition without generating a system reserved partition or system recovery partition. The only way to prevent Windows from creating another partition is to partition hard drive before installing.

Partition a hard drive during Windows setup

Windows build-in tool, Disk Management or Diskpart.exe can be used for hard drive partitioning. Disk Management can only be used when OS has been successfully loaded, so you can use Disk Management to create a new partition for another OS if you already have windows installed. If you want to create partition without Windows pre-installed on the hard drive, you can use a Windows installation disc to run Diskpart. The specific steps listed below:

1. Insert the installation disc, and boot your computer from it.

2. At the Windows Setup screen, press Shift+F10 simultaneously to open a command line prompt. If you use the New button to create partitions, it will generate a system partition for an MBR disk.

3. Type “diskpart” and press Enter.

4. At Diskpart>, run a few lines of commands to create a new partition:

в—† List disk
в—† Select disk [disk number]
в—† Create partition primary [size=n]

For example, the following command is to create a 30000 MB primary partition on disk 0:

в—† List disk
в—† Select disk 0
в—† Create primary partition size=30000

5. Then you will have created a partition around 30GB. You can use this command to create more partitions or exit.

If your hard drive has enough space, then it is recommended to allocate more than 100GB to the system drive because Windows update, installed programs, and other system files will keep consuming space on system partition. If you don’t have a Windows installation disc, then you can use third-party free partition manager software to create partition without operating system.

Create partitions without OS pre-installed with free partition manager

AOMEI Partition Assistant Standard is a freeware for disk and partition management that provides the ability to create bootable media, so you can partition a hard drive with or without OS pre-installed. If you have Windows installed on your hard drive, you can just free download this software and start to partition your hard drive without losing data. Let’s see how it works:

1. Boot your computer from the AOMEI bootable media you created. It will lead you to the main interface of AOMEI Partition Assistant.

2. Right-click on unallocated space or a partition that is big enough to create a new partition, and then choose Create Partition button.

3. At the next screen, drag the slider or enter the amount of space to specify the partition size. You can also click Advanced option to see more options. Click OK when settings are done.

4. The program allows you to preview the partition layout without making any changes to your hard drive. If no problem, click Apply to run the operations.

It is really a good shot to create partition before installing another OS on your hard drive. Besides NTFS, AOMEI Partition Assistant also supports many other file systems including FAT32, FAT16, FAT12, exFAT, ReFS, and Ext2/Ext3/Ext4. The paid edition, like AOMEI Partition Assistant Professional or AOMEI Partition Assistant Server, provides even more advanced features like enabling you to migrating OS to GPT disk, converting dynamic disk into basic, etc.