Can't extend C drive volume in Windows 10

by John, Updated on: March 3, 2021

This article explains why can't extend volume in Windows 10/8/7 Disk Management and what to do when cannot extend C drive for Windows 10 laptop/desktop.

Nowadays, many Windows 10 computers use SSD for Operating System and programs. It is helpful to improve computer performance. However, comparing with traditional mechanical disk, SSD is much smaller because it is still expensive. So the partitions are more likely running out of space, especially to the system C drive.

From Windows 7, new Extend Volume function was added in Disk Management to help extend partition without losing data. However, this function only works under specific condition. Windows 8/10 inherited the same function without improvement, so many people encounter issue while extending partition. The typical example is that Disk Management cannot extend C drive after shrinking D. In this article, I'll explain all probable reasons why cannot extend volume in Windows 10/8/7 Disk Management, and how to solve this problem fast and easily.

Why can't extend C drive in Windows 10/8/7 Disk Management

Reasons 1: no Unallocated space next to C drive

In a Windows computer, there are 3 types of space on a hard disk:

In Windows 10/8/7 Disk Management, Unallocated space can be used to create new volume or combined to other partition. To get Unallocated space, you may either delete or shrink a partition. Because the size of a physical disk is fixed, before extending a partition, you must delete or shrink another partition to get Unallocated space. Without such kind of space, of course you cannot extend partition in Windows 10/8/7 Disk Management.

Obviously, it is better to get Unallocated space by shrinking a partition, because you won't lose files in it. The problem is, you can't extend C drive in Windows 10/8/7 even after shrinking D or any other partitions, because Disk Management has many shortages.

This is the most common reason why can't extend C drive in Windows 10/8/7 Disk Management. As you see in the screenshot, I cannot extend C: drive and E: drive after shrinking D. Because, C drive is nonadjacent to the Unallocated space, E drive is on the right.

Extend Volume greyed out

Reasons 2: the contiguous partition is Logical

Because I can't extend C drive in Windows 10/8/7 Disk Management after shrinking D, I tried to delete the adjacent D drive in my test computer. As you see, Disk Management is still unable to extend C drive.

After deleting D

After deleting E

Why there's such strange issue?

MBR GPT disk

In Windows computer, there are 2 types of disk - GPT and MBR. On GPT disk, all partitions are created as Primary. But on MBR disk, there could be Primary and Logical partition. In addition, you can only create maximum 4 Primary partitions, or 3 Primary partitions plus an Extended partition on MBR disk.

Primary partition works as an independent unit, but Logical partition is part of the Extended partition. After deleting a Primary partition, its disk space will be changed to Unallocated, but after deleting a Logical partition, it will be changed to Free space.

While extending partition in Disk Management, Unallocated space can't be extended to any Logical partition. Free space can't be extended to any Primary partition. In a word, if you want to extend C drive by deleting D in Disk Management, D must be Primary partition, because C drive is always Primary. (Note: D drive in this article means the contiguous partition behind C drive.)

What to do when cannot extend C drive partition

Follow corresponding solution according to your own disk partition configuration.

Solution 1: move partition and Unallocated space

As I explained above, Disk Management can't extend C drive partition when Unallocated space is nonadjacent. Therefore, you need to move Unallocated space from right side of D to the left.

Steps when can't extend C drive in Windows 10/8/7 after shrinking D:

Step 1: Download NIUBI Partition Editor, right click D: drive and select "Resize/Move Volume", drag the middle towards right in the pop-up window.

Move drive D

Then Unallocated space is moved next to C drive.

Move Unallocated

Step 2: Right click C: drive and select "Resize/Move Volume" again, drag right border towards right in the pop-up window.

Extend C drive

Then C drive is extended by merging this Unallocated space.

Extend volume C

This program is designed to work in virtual mode to avoid mistake, to modify real disk partition, you need to click Apply on top left to take effect.

Watch the video how to move Unallocated space and add to C drive:

Video guide

Solution 2: shrink and extend partition with NIUBI

If the contiguous partition D is a Logical drive, as I explained above, Disk Management is unable to extend C drive by either shrinking or deleting D. It is very easy to solve this problem with NIUBI Partition Editor.

  1. Right click D and select "Resize/Move Volume", drag left border towards right in the pop-up window, then Unallocated space is made on the left.
  2. Follow step 2 above to merge Unallocated space to C drive.

Other reasons why cannot extend volume in Windows 10/8/7

When you extend a data partition via Windows Disk Management, you may encounter additional issue.

  1. FAT32 partition can't be extended even if there's contiguous Unallocated space on the right. Disk Management can only extend NTFS partition.
  2. Disk Management cannot extend volume beyond 2TB on a MBR disk.

Additional solutions when cannot extend volume in Windows 10/8/7 Disk Management:

  1. To NIUBI Partition Editor, there's no difference if you want to extend FAT32 or NTFS partition. So, you just need to follow the method above to combine contiguous Unallocated space.
  2. To extend a volume larger than 2TB, convert MBR disk to GPT in advance with NIUBI.
  3. If you want to extend the right partition E after shrinking D, you just need to run "Resize/Move Volume" for E drive and drag left border towards left in the pop-up window.

Drag to extend

Besides helping fix the issue that can't extend volume in Windows 10/8/7, NIUBI Partition Editor helps you do many other disk partition management operations such as copy, convert, merge, defrag, wipe, hide partition, scan bad sectors, etc.