By Teresa / Last Updated April 15, 2021

When need to repartition a hard drive?

When you have different plans for a used hard drive, you may need to repartition it. Repartitioning a hard drive means you’ll re-allocate partition size, drive letter and file system. Generally speaking, you may want to repartition a hard drive in following situations.

▶Resize partition. A general repartition could be simply resizing existing partitions to satisfy your new need. Resize to generate unallocated space and then create new partition with that space, or add it to another space-needing partition.

▶Partition hard drive for Mac and PC Windows. It is necessary to do repartitioning if you’d like to install dual-boot operating systems. You’ll need at least two primary partitions that are large enough and formatted with different file systems to store the OS. Except for Mac and Windows, many users tend to dual boot Windows 7 and Windows XP, Windows 10 and Windows 7, etc.

▶Partition hard drive before installing Windows 7. You may want to partition a hard drive before you install a new operating system. Sometimes, the behavior solves the issue that hard drive is not recognized while installing Windows.

You may need to repartition a hard disk under other situations that haven’t been listed here. However, what counts next is to figure out how to repartition a hard drive for the best.

2 General ways to repartition hard drive in Windows 10/8/7 

Windows brings you internal device manager that allows you to partition hard drive in Windows 10/8/7. You can complete the task with the help of Disk Management or Diskpart. Let’s take a closer look at how they work.

Method 1. Repartition hard drive in Disk Management

Right click My Computer, Computer or This PC and select Manage to open Disk Management. You’ll see partition status, drive letter, file system, used space and other necessary factors right there.

1. To extend partition: if there is unallocated space adjacent to the partition you want to extend, you can do the extending. Right click the partition and select Extend Volume. Follow the wizard to perform extending.


If there is no contiguous space next to that partition, or even no unallocated space on that disk, you’ll find Extend Volume grayed out.

2. To shrink partition: right click the partition and select Shrink Volume. You should be able to shrink the partition to half of the partition size. If you want to shrink a partition size more than a half, you need to turn to the third-party software.


3. To create new partition: right click an unallocated space and select New Simple Volume. Follow the wizard to complete the creating. You can get unallocated space by deleting existing partitions, but be sure to back up important files before you start.

New Simple Volume

If you want to completely repartition a hard disk, you can delete all existing partitions to let the unallocated space into one. Then, do the dividing and creating. Nevertheless, that can be done on the external hard drive only because Windows does not allow you to delete system partition under Windows environment. It also goes to formatting a partition with another file system.

Method 2. Repartition hard drive Command Prompt

You can do hard drive partitioning using CMD, a more direct method for advanced users.

1. Press Windows key + R key to open Run. Type diskpart and run as administrator.

2. To resize partition, type: list volume > select volume n (where n is the number of the partition you want to change) > extend size=10240 (in MB) > exit. You can replace extend with shrink. Each command needs to be followed by pressing "Enter".

Diskpart Extend C Drive

3. To format a specific partition, type: format fs=ntfs (or fat32) after you select the drive.

Diskpart Format Fat32

You can type: /? to see what diskpart can do for you. Generally, more options than Disk Management can offer. For more information about diskpart.exe, check out Diskpart Windows 10.
To extend a partition via CMD, there must be an adjacent unallocated space right after the aim partition (same as the Disk Management), otherwise, it will fail and prompt error message.

Best way to repartition hard drive without losing data

Using Disk Management and DiskPart to repartition a hard drive in Windows PC, you can only shrink or extend NTFS partition. Besides, the “Extend Volume” option only works when there is contiguous unallocated space on the right side of the target volume. Moreover, all operations have risk of losing stored data. To be specific, to give a drive with different file system, you need to format it. To add unallocated space to a non-adjacent partition for extending, you need to delete the partition between the target partition and unallocated space.

To get around all those limitations and risks, you can switch to a professional disk partition manager named AOMEI Partition Assistant Professional (Windows 10/8/7/XP/Vista supported). It allows you to:
allocate free space from one partition to another directly with no need to shrink and then extend; create new partition directly from existing redundant partition;
change file system without formatting between NTFS and FAT32;
quick partition a hard drive with several partitions in one click;
partition internal disk without booting Windows with created bootable media; and more.

You can download the demo version and check out how it resizes drives:

Download Free Demo Win 10/8.1/8/7/XP
Secure Download

Step 1. Install and run AOMEI Partition Assistant Professional. You will get the main interface. Right-click on the volume D or the drive you want to reallocate. Then, select "Resize Partition".

Resize D Partition

Step 2. Drag the bar to release some free space. After that, select "OK".

Shrink D Partition

With the unallocated space, you can directly create a new partition: Right click the unallocated space and select "Create partition" and follow the prompts. Or you can use it to extend another partition like C drive. To do so, you can first move D partition to the right side to make unallocated space contiguous and behind C drive, and then add it into the C partition:

Step 1. Right click D drive and select "Move Partition",move it to the right side to make unallocated space next to C drive.

Move D Partition

Step 2. Then right click C drive and select "Resize Partition". Drag the bar to the right side to add into the unallocated space.

Resize C Partition

Step 3. Back to the main interface, click "Apply" to commit the pending operation.


With this Professional edition, you can also merge non-adjacent unallocated space into another partition directly no matter where it is located on the disk via the "Merge Partitions" feature.

Add Unallocated Space To C Drive

As stated, you can quick partition a hard disk into several different partitions simultaneously. Right click the disk you want to partition and select Quick Partition from the given list. You’ll see a window below. Configure each partition as you wish.

Quick Partition


In this article, we have shared 3 tools to repartition hard drive in Windows 10/8/7. If you want to repartition hard drive without formatting or losing data, AOMEI Partition Assistant Professional is the best chioce. For users to manage hard disk and reallocate a hard drive in Windows Server 2000/2003/2008/2012/2016/2019, you can use AOMEI Partition Assistant Server Edition, a server partition magic.