Extend Volume greyed out

Can’t extend C drive with Unallocated space

This article explains why cannot extend C drive volume with Unallocated space in Disk Management and what to do when you are unable to expand C drive with Unallocated space in Windows 10/8/7 and Server 2019/2016/2012/2008 (R2).

Why cannot extend C drive with Unallocated space

From Windows Server 2008, Microsoft added GUI Extend Volume functionalities in native Disk Management console. It is easy and fast, but meanwhile it has some limitations that cause Extend Volume doesn’t work.

In fact, Extend Volume does not support FAT16/32 partitions. However, it is not an issue to system C drive, because it is formatted as NTFS by default. The most common reason why you are unable to extend C drive with Unallocated space is because this space is nonadjacent.

From Microsoft, Extend Volume only works when there is adjacent Unallocated space, in addition, this space must be on the right side. To show you this restriction, I shrank drive D with another Shrink Volume functionality.

Extend Volume greyed out

As you see:

  • Only drive D fits for the requirement, so Extend Volume is available.
  • I can’t extend C drive, because the Unallocated space is nonadjacent to it.
  • I can’t extend drive E with Unallocated space, because Unallocated is on the left side.

What to do?

In fact, it is very easy to solve this problem, you just need 1 step to move Unallocated space to the other side.

Download NIUBI Partition Editor, you’ll see all disk partitions on the right and available operations to highlighted disk or partition on the left side.


Right click drive D and select “Resize/Move Volume”, drag the middle position towards the other side in the pop-up window.

Move D

Click OK, 20GB Unallocated space is moved to the left side of D.

Unallocated moved

Tip NIUBI Partition Editor is designed to work in virtual mode, to modify real disk partition, you need to click Apply to take effect. If you changed your mind, simply click Undo to cancel the pending operations.

After this operation is completed, Extend Volume is enabled for C drive. You may either expand C drive in Windows Disk Management or continue with NIUBI.

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

Extend C

Click OK, Unallocated space is combined to C drive. Remember to click Apply to take effect.

System drive extended

Because of the limitation of Extend Volume, Disk Management cannot extend C drive with Unallocated space that shrinking from D or other partitions. With NIUBI Partition Editor, you can extend a volume by combining Unallocated space on either side. When the Unallocated is nonadjacent, simply move it and then combine.