By Teresa / Last Updated May 25, 2020

Why move unallocated disk space to C drive?

Unallocated disk space refers to the unused hard drive space on your disk. It won’t show up in Windows Explorer, yet you can check if you have unallocated space in Disk Management by typing diskmgmt.msc in Run box. Moving unallocated space to C drive in Windows 10, 8, 7 is good way to enlarge system drive, so that you can install more programs there and keep other programs function well. The performance of your system drive will directly affect the function of your running operating system and software, games in particular. More free space makes creating personal files easier.

Some computers are come with small-sized system drive when produced by manufacturers. If there is plenty of free space in other partitions like D, E, you can allocate free space from each partition to C drive directly. All in all, you may hold other factors that force you to extend the system drive. The most important thing is to find how to move unallocated space to C drive using the simplest method.

How to allocate unallocated disk space to C drive in Windows 10/8/7?

The method you choose to add unallocated space to C drive is determined by the location of unallocated disk space. Generally speaking, you have three ways to complete this task, built-in Disk Management, Diskpart and third-party software.

Add unallocated space to C drive in Disk Management

As covered before, the location of the unallocated space affects your choice. If it is next C drive and at the right side of C drive, you can add it to system drive i.e. C drive directly in Disk Management. Open Disk Management by following aforementioned approach. Right click C drive and select “Extend Volume” in the menu. The only thing left to do is following the wizard to resize system partition.

Extend Volume

Transfer unallocated space to C drive via Diskpart

Likewise, you can directly extend C drive to the unallocated space when the space is adjacent to C drive. Let’s get to know how to work this out using CMD.

1. Press Windows key plus R key to open Run. Type diskpart and press Enter. Run as administrator.

2. Type following commands in turn and each command has an Enter followed by.

  • list volume

  • select volume c (or select volume 1)

  • extend (or extend size=10240 which means you’ll extend by 10GB in size)

  • exit

Diskpart Extend C Drive

That is a simple method of combining unallocated space to C drive as well. However, what if the unallocated space is separately distributed on the hard drive, for example, the unallocated space after D drive in the screenshot? If you right click C drive this time, only to find the “Extend Volume” grayed out. And you’ll get Diskpart failed to extend the volume error in Diskpart. Otherwise, you need to delete the in-between partition, extend C drive and then restore the partition. Anyway, that is when you have to turn to third party partitioning software.

AOMEI Partition Assistant Professional will assist you merge all unallocated disk space on the hard drive to C drive without formatting or deleting any partitions. The unallocated space generated after cloning could also be managed with it. You can even allocate free space to C drive from existing partition with it. Moving unallocated space to left or right side is also available.

It has graphical and clean user interface and is suitable for all PC users vary from novices to professionals. Download to learn how to merge unallocated space to C drive in Windows 7, for instance.

Move unallocated space to C drive without deleting partition

Step 1. To add non-contiguous unallocated space to c drive, install and start AOMEI Partition Assistant. Right click C drive and select “Merge Partitions”.

Merge Partitions

Step 2. Check all unallocated space as well as system drive.

Select Unallocated Space

Step 3. Confirm the virtual outcome. Click “Apply” to execute the operation.


There is one final confirmation, just click “Proceed”.



  • Since there is system drive involved in this operation, it will complete allocating in restart mode.

  • You can move unallocated space to primary partitions by repeating those methods as well.

  • To add unallocated space to C drive in Windows Server 2008/2003/2012 without deleting, please refer to AOMEI Partition Assistant Server Edition.

Believe it or not, you have successfully moved unallocated space to C drive in Windows OS with AOMEI Partition Assistant. You have options to merge data partitions say D, E drive to system drive as you wish using the same feature. As a matter of fact, AOMEI Partition Assistant is capable of many other things, for example, you are allowed to install Windows 10 on external hard drive with “Windows to go Creator” wizard. When upgrading hard drive, the “migrate OS to SSD” wizard matters a lot. You may also make SanDisk USB bootable with “Windows To Go Creator” wizard and realize BYOD.