On a BIOS-based computer, you can divide each disk into as many as four standard partitions.

Typically, these standard partitions are designated as primary partitions. Primary partitions can be used to store files.

The computer boots to the active partition. You can designate only one primary partition as active.

On the default Windows 7 and Windows Server 2008 R2 configurations, the active partition is typically a separate partition called a system partition. System partitions are described later in this topic.

The following diagram shows the default Windows 7 and Windows Server 2008 R2 partition structure:

To use more than four partitions:

1. Designate one of the four standard partitions as an extended partition.
   
   An extended partition is a special partition that can be divided into additional partitions called logical partitions. You can divide the extended partition into as many logical partitions as can fit on your disk.
   
   An extended partition cannot store files; it can store only logical partitions.
   
   
2. Add logical partitions to the drive.
   
   Logical partitions can store data.
   
   

The following diagram illustrates an example of a disk partition structure that includes primary, extended, and logical partitions:

On a Unified Extensible Firmware Interface (UEFI) computer, drives may include:

1. An Extensible Firmware Interface System Partition (EFI System Partition, or ESP).
   
   Each bootable drive must contain an ESP.
   
   System partitions (such as the ESP) are described later in this topic.
   
   
2. A Microsoft® Reserved Partition (MSR).
   
   This is recommended for all drives.
   
   
3. Up to 128 primary partitions. Primary partitions can be used to store files.
   
   

Each bootable drive must contain an operating system, such as Windows.

The following diagram shows the default Windows 7 and Windows Server 2008 R2 UEFI-based partition structure:

For more information about UEFI disks and hard disk partitions, see The Windows and GPT FAQ.

The computer will boot to the Extensible Firmware Interface System Partition (EFI System Partition, or ESP).

Basic system partition requirements are:

• Must have at least 100 megabytes (MB) of hard drive space.
  
  
• Must have enough free space to create shadow copies of the partition.
  
  
  • 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 gigabyte (GB), we recommend that it should have at least 1 GB free.
    
    

  	Note:
  	We recommend that no other files are placed on the system volume, and we recommend that you discourage end-users from storing files on this partition, to avoid filling up this space.

• Must be configured as the active partition.
  
  
• Must not be an encrypted partition.
  
  
• Must be formatted as NTFS for BIOS-based systems. (For file-system recommendations for UEFI-based systems, see the MSDN topic: Choosing a file system: NTFS, FAT, or FAT32.)
  
  

Notes

To discourage users from accidentally modifying or deleting the partition: Identify the partition as a utility partition. Utility partitions do not receive a drive letter. To do this, set the unattended setting: Microsoft-Windows-Setup\DiskConfiguration\Disk\ModifyPartitions\ModifyPartition\TypeID to 0x27 on BIOS-based systems, or e3c9e316-0b5c-4db8-817d-f92df00215ae for UEFI-based systems. Add a label to the partition. This helps users identify the partition when viewing the disk with tools such as Computer Management.

Additional requirements for BitLocker

BitLocker increases protection for your computer by running Windows in a separate, encrypted data partition.

When BitLocker is installed, the following are additional requirements for the system partition:

• The partition must be separate from the Windows partition.
  
  

For more information, see Understanding BitLocker Drive Encryption.

Additional requirements for Windows RE

Windows RE can help users recover from critical system failure.

You can install Windows RE in the system partition, in the Windows partition or in a separate recovery partition.

When Windows RE is installed on the system partition, the following are additional requirements for the combined partition:

• The partition must be physically located in front of all user partitions.
  
  
• Must have an additional 200 MB of hard drive space for Windows RE files.
  
  Example: System + Windows RE files = 300 MB
  
  
• Must not be used to store user files.
  
  

When Windows RE is installed on a separate partition, the following are additional requirements for the Windows RE partition:

• Must have enough free space to create shadow copies of the partition.
  
  
  • 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.
    
    
  • Must not be used to store user files.
    
    

For more information, see Understanding Windows Recovery.

For information about deploying Windows RE, see Deploy a System Recovery Image.