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How to Create a Fourth Primary Partition in Windows 7 or Vista

Summary: First use Windows' Disk Management to create Unallocated space (RAW) on the hard disk. Next use Diskpart at a command Prompt to create the 4th Primary partition. Finally use Windows' Disk Management to Format, and allocate a drive letter to, the new Primary partition. A detailed explanation follows.

Note: If you have four Primary partitions, you cannot create any further (even Logical) partitions on that hard disk.

First create Unallocated space by Shrinking an existing volume on the Hard Disk

1. Restart computer correctly (close all programs before you Restart computer).
2. Open Disk Management in Windows 7/Vista (right-click Computer, select Manage, click Disk Management).
   • Right-click the Primary partition to need to shrink in size, and click Shrink Volume
     (you can shrink any Primary that's not Hidden in Windows Explorer).
     • In Enter the amount of space to shrink in MB: enter enough for the new Primary.
     • Click the Shrink button (it will take some time to complete!).
   
   If Shrink does not give you sufficient Unallocated space, read Shrink the Windows 7 or Windows Vista Partition (new window) for instructions on how to complete this task successfully. Then return here.

Next use Diskpart at a Prompt to create the fourth Primary partition in the Unallocated space.

Warning: You must have created Unallocated space (RAW) on the selected hard disk before you continue.

1. Backup important data - just in case!
2. Right-click the Command Prompt shortcut and click Run as administrator
   (Start > All Programs > Accessories > Command Prompt).
   Click Yes if asked for User Account Control or enter your password.
   • Type DISKPART at the Prompt and press Enter.
   • Type LIST DISK at the Diskpart prompt and press Enter
     - note the disk number for your new Unallocated space (Disk 0=1st hard disk, Disk 1=2nd, Disk 2=3rd).
   • Type SELECT DISK Z, where Z is the number you just noted.
   • Type CREATE PARTITION PRIMARY
     - all the Unallocated space will be used for the new Primary.
   • Type EXIT to exit Diskpart.
   • Type EXIT to exit Command Prompt.

Finally Format the new Primary partition with Disk Management.

1. Open Disk Management in Windows.
   You'll see the new partition is a fourth Primary and is in a RAW state without a drive letter.
   • Right-click that partition, select Change Drive Letter and Paths..., and Add a drive letter to it.
   • Right-click that partition again and Format all of it (usually with the NTFS file system).