Extend system partition

Extend system partition on Windows 10

To many computer users, System partition is the drive that Operating System is running from, that is C: drive. Comparing with data drives, system partition is more likely running out of space. In addition, you can easily transfer files of data drives to other place, but to system partition, it is much more complicated. This is the reason why many people want to extend system partition. However, there is a key point that whether it is safe.

Actually, you can extend system C: drive but it may cause Windows damage or data loss if you use unreliable tools.

In this article, I’ll show you how to extend system partition drive in Windows 10 without reinstalling or losing any data.

Extend system partition

Difference between System and Boot partition

To many computer users, System partition is the drive that Operating System is located, but it’s wrong.

  • The System partition is a primary partition that contains the files for booting Windows, files include Ntldr, Boot.ini, Ntdetect.com, bootmgr, BCD, etc.
  • The Boot partition is the partition where Windows is installed, it contains the operating system folder/directory.

Before Windows 7, system and boot partition are the same one and both are given “C:” drive letter. But from Windows 7, new added BitLocker requires an unencrypted partition, so System partition is separated from C drive.

System Boot partition

Never mind, no matter you want to extend system partition or boot C drive in a MBR disk, you can accomplish with NIUBI Partition Editor. But you can only extend boot partition C in a GPT disk, you cannot extend system reserved partition on Windows 10.

To avoid misunderstanding, the same with other people, I indicate system partition as C drive.

Extend system partition with Disk Management

Windows 10 Disk Management inherited Shrink Volume and Extend Volume from Windows 7, so you can change size of allocated partition with these functionalities. However, both supports NTFS partition only. It is not an issue when extending system partitions, because they are formatted as NTFS by default when installing. But there is another serious limitation that cause you cannot extend system partition C.

When shrinking the adjacent drive (D:) with Shrink Volume, Unallocated space can only be produced on the right side, but to expand C drive with Extend Volume, Unallocated space must be on the left side of D. You may delete drive D to get adjacent Unallocated space on the right side of C, but programs are installed in D drive, so you cannot do this.

If programs are not installed in drive D, you may follow the steps below to extend system drive C:

  1. Transfer all files in drive D to other partition.
  2. Press Windows and X on keyboard and then click Disk Management.
  3. Right click drive D and select Delete Volume.
  4. Right click drive C and select Extend Volume.
  5. Simply click Next to complete the Extend Volume Wizard.


  • If there are some Windows services running from D, these services will stop working after deleting, so be caution about this operation.
  • If this hard disk is MBR and drive D is a Logical partition, you still cannot extend C drive by deleting D.

Extend system drive with partition software

Comparing with Windows 10 native Disk Management, third party professional partition software is much more powerful without these limitations. However, not all partitioning software can accomplish this task well. In fact, there is potential system and data damage risk, because all parameters of related disk, partition and files must be modified absolutely correct. If any software error or hardware issue such as power outage occur when you resizing and extending disk partitions, part of the parameters cannot be modified, so system and/or data will be damaged.

Better that other tools, NIUBI Partition Editor provides unique 1 Second Rollback technology to ensure system and data intact. If anything goes wrong during these process, it reverts the computer to original status automatically and rapidly. Furthermore, thanks to its special file-moving algorithm, it is much faster than any other tools. So it is always recommended if you want to shrink and extend hard drive on Windows 10 and previous versions.

How to extend system partition on Windows 10 with NIUBI:

Actually, it is very easy and you just need to drag and drop on the disk map.

Download NIUBI Partition Editor and you’ll see all connected disks with graphical partition configuration on the right side. In my Windows 10 laptop, C drive is 30GB and D is 50GB.

NIUBI main window

Step 1: right click drive D and select Resize/Move Volume. Drag left border rightwards in the pop-up window, or enter an amount manually behind “Unallocated space before“.

Shrink D drive

Click OK, drive D is shrank to 30GB and 20GB Unallocated space is produced on the left side.

Unallocated generated

Step 2: Right click C drive and select “Resize/Move Volume” again. In the pop-up window, drag the right border rightwards.

Extend C drive

C drive is extended to 50GB by merging the 20GB Unallocated space. Click Apply on top left to execute, done. The pending operations with  can be done in Windows without rebooting.

C drive extended

If there is not plenty of free space in the adjacent drive D, you can shrink other drive and move the Unallocated space to the right side of C drive. Then extending the system partition C is as easy as a piece of cake. Watch the video:

In Summary

Windows 10 has built-in Shrink and Extend Volume functionalities to change partition size, but because of the limitations, they are useless. To extend system partition on Windows 10, you still need 3rd-party tools. Because of potential system damage and data loss risk, you’d better back up and use the safe disk partition software such as NIUBI Partition Editor.

Download to try