How to Merge Unallocated Space to C: Drive in Windows Server/PC

By John, Updated on: May 24, 2022

Besides creating new volume, Unallocated space can be combined to partition to increase free space. To get Unallocated space, you may either shrink or delete a partition. In Windows 11/10/8/7 and Server 2022/2019/2016/2012/2008, there are "Shrink Volume" and "Extend Volume" functions in Disk Management. Some people try to shrink D and extend C drive with this native tool but failed. Because after shrinking D drive, Disk Management can't merge Unallocated space to C drive. In this article, I'll introduce how to merge Unallocated space to C drive in Windows server and PC easily and safely.

Applies to: Windows 11, Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, Windows Server 2022, Windows Server 2019, Windows Server 2016, Windows Server 2012 (R2), Small Business Server 2011, Windows Server 2008 (R2) and Windows Server 2003 (R2).

1. Why Disk Management can't merge Unallocated space to C drive

C drive low disk space is common issue in both Windows PC and server. When it happens, nobody likes to waste a long time to reinstall everything or recreate partitions and restore everything from backup. Therefore, many people want to expand C drive without losing data. It is easy to shrink D or other partition to get Unallocated space with Disk Management, but you'll find that this Unallocated space can't be combined to C drive, because Extend Volume is always grayed out.

Why Windows Disk Management cannot merge Unallocated space to C drive:

As you see in the screenshot, after shrinking D drive, Unallocated space is made on the right of D, Disk Management cannot merge this Unallocated space to nonadjacent C drive or to the right partition E.

Extend Volume greyed out

To merge Unallocated space to C drive in Windows PC and server, NIUBI Partition Editor is better choice. It is able to combine Unallocated space to either contiguous partition by 1 step. When Unallocated space is nonadjacent, this software can move Unallocated space adjacent to the partition and then combine. It has free edition for Windows 11/10/8/7/Vista/XP home users.

2. How to merge Unallocated space to C drive with free partition editor

Download NIUBI Partition Editor and you'll see the main window with disk partition structure and other information. There's 20GB Unallocated space which is shrunk from D: drive.

NIUBI Partition Editor

Steps to merge Unallocated space to C drive in Windows 11/10/8/7/Vista/XP:

  1. Right click D: drive and select "Resize/Move Volume", drag the middle of D drive towards right in the pop-up window, then Unallocated space is moved to the left.
  2. Right click C: drive and select "Resize/Move Volume" again, drag right border towards right in the pop-up window, then Unallocated space is combined to C: drive.
  3. Click Apply on top left to confirm and execute. (Real disk partitions won't be modified until click Apply to confirm.)

Follow the steps in the video:

Video guide

To merge Unallocated space to C drive in Windows Server 2022/2019/2016/2012/2008/2003, the steps are the same, but you need server or higher edition.

Better than other tools, NIUBI Partition Editor has Virtual Mode and Cancel-at-well technologies to avoid incorrect operations. Advanced file-moving algorithm to help move partition much faster. Unique 1-Second Rollback technology to protect system and data. If any error is detected, it automatically reverts computer to original status in a flash.

3. Combine Unallocated space to C drive with another disk

In some computer, there's not enough free space on the same disk. Some people shrunk a partition on another disk and want to combine to C drive. It is impossible with any partitioning software, because the size of a physical disk is fixed. If free or Unallocated space can be transferred to another disk, the size of both disks will be changed.

When there's no available free space on the system disk, you have 2 options to extend C drive:

  1. Move a data partition to another disk, delete it and combine its space to C drive.
  2. Copy whole system disk to a larger one and extend C drive with extra disk space.

If you use virtual machine, it's much easier, follow the steps to expand virtual disk in Hyper-V or VMware, and then merge additional Unallocated space to C drive.

Besides move partition and merge Unallocated space to C drive in Windows 11/10/8/7/Vista/XP and Server 2022/2019/2016/2012/2008/2003, NIUBI Partition Editor helps you do many other disk partition management operations such as copy, convert, wipe, defrag, hide partition, scan bad sectors and optimize file system.