How to Reallocate Disk Space from D to C drive in Windows 10/8/7?

If you want to reallocated disk space from one drive to another (like D drove to C drive), here you can learn the best way to allocate hard drive space from one partition to another partition in Windows 10, 8, 7.


By Emily / Updated on May 12, 2023

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Why do you need to reallocate disk space?

C drive is allocated while you are installing Windows operating system. However, the C drive is easy to get full in a certain time, that’s because many kinds of files are adding into it constantly such as the Windows updates, Windows Services, Windows files, applications and other default output path. When the C drive is almost full and prompts low disk space warning, many issues will be triggered. For example, the OS reboots and runs much slower or even crash.

Therefore, you might want to know how to reallocate disk space to make the C drive bigger. In this article, we will share all possible methods to redistribute disk space without repartitioning hard disk or losing any important data in Windows 10, 8, 7.

Can you redistribute disk space between partitions via Disk Management?

When it comes to reallocating hard disk space, most users think of Disk Management (one of Windows native disk management tools). It allows you to shrink partition to generate some unallocated space, with which you can only create a new partition. You cannot extend C drive with the unallocated space from shrinking another partition (like D drive). If you do that, you will find the "Extend Volume" option is greyed out.

Extend C Volume Grey Out

Why? That’s because Disk Management can only extend a partition when it is followed by an adjacent unallocated space whereas shrinking a partition can only generate a piece of unallocated space on its right side.

Best way to reallocate disk space in Windows 10/8/7

To easily and flexibly reallocate hard drive space from one drive to another, the best way is to make use of a third-party partition manager like AOMEI Partition Assistant Professional. This partition software is compatible with all editions of Windows 10/8/7 and Windows XP/Vista (either 32-bit and 64-bit). If you have shrunk another partition to get unallcoated space for extending C drive in Disk Management, you can use this software to move the partition (that is shrunk) to the right side and make the free space adjacent to the c drive, and then you can extend the system partition in Disk Management.

Move Partition

Besides this advanced function, AOMEI Partition Assistant Professional also provides the following amazing features to help Windows PC users to reallocate disk space flexibly:

☪1. Merge Partition: it is able to directly merge unallocated space into another partition (no matter they are contiguous or not), and merge two adjacent partitions into one.
☪2. Allocate Free Space: it can directly allocate some free space from one drive to another by 3 steps. Quite easy and safe.
☪3. Extend Partition Wizard: the wizard can extend system and any other data partitions without restarting your PC.

Step-by-step guide: how to reallocate disk space from D to C

Now, we will demonstrate how to reallocate disk space from D drive to C drive via “Allocate Free Space” function (as an example) step by step. You can download the demo version for a free trial here.

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

Step 1. Install and launch AOMEI Partition Assistant Professional. Right click the D drive or other partition that has enough free space and select “Allocate Free Space”.

Allocate Free Space

Step 2. In this window, you can input how much free space to allocate to C drive and click “OK”.

Allocate From D To C

Step 3. Back to the main interface, click “Apply” and “Proceed” to commit the pending operation.

Apply Allocate Free Space

Wait for a while and the free space will be allocated from D drive to C drive. If you delete all partitions on the hard disk and want to reallocate disk space, you can make use of “Quick Partition” function to divide a disk into several partitions within one click.

Quick Partition


Now, you must have gotten the best method of how to reallocate disk space from one drive to another one in Windows 10/8/7. In addition to partitioning hard disk flexibly, AOMEI Partition Assistant also has some other fantastic functions: transfer only OS to SSD, convert (boot) disk to MBR or GPT without deleting partitions and losing data, clone hard disk or partition and more. To manage disk partition with those functions on Windows Server operating system, you can try AOMEI Partition Assistant Server.

Emily · Staff Editor
Emily is an English editor of AOMEI Technology; she has a great passion for providing easy solutions for people to tackle with all disk or partition management problems. In addition to writing articles about disk/partition management, she also edits great tutorials on how to back up and restore disk for data security. In her spare time, she loves to learn computer skill to improve herself or stay with her family to enjoy a good day.