Solution - unable to extend C drive in Windows 10/8/7

by James, Updated on: March 26, 2021

C drive low disk space is common issue in Windows laptop and desktop, to solve this problem, many people want to expand C drive without installing operating system and all programs. From Windows 7, Microsoft added new Shrink Volume and Extend Volume functions in Disk Management to help change partition size without losing data. However, both functions have shortages. Windows 8/10 inherited the same functions without any improvement, so you'll encounter many issue if you want to increase C drive space with this native tool. This article introduces why you are unable to extend C drive volume in Windows 10/8/7 Disk Management and how to solve this problem easily.

Why unable to extend C drive in Windows 10/8/7 Disk Management

Reason 1: There's no contiguous Unallocated space on the right

Firstly, you should know that the size of a physical hard disk is fixed, so before extending a volume, there must be Unallocated space. To get such kind of space, you may either delete or shrink another volume on the same disk. The same with the screenshot, Extend Volume is greyed out for every drive if there's no Unallocated space on this disk.

Better than deleting a volume, you can get Unallocated space by Shrink Volume function without losing data. Many people did this in Disk Management but found that they are still unable to extend C: drive in Windows 10 Disk Management after shrinking partition D, why?

No adjacent space

If you have tried to shrink D drive, you'll know that Shrink Volume function only gives you an option to enter an amount of space, and then Unallocated space is made on the right. You cannot specify the location to make on the left.

Another major shortage of Disk Management is that Extend Volume function can only extend Unallocated space to the contiguous partition on the left. As you see in the screenshot, after shrinking D drive, E drive is on the right and C is non adjacent to the Unallocated space, therefore, Extend Volume is disabled for both partitions.

This is the most common reason why Disk Management is unable to extend C drive in Windows 10/8/7.

Extend Volume greyed out

Reason 2: The contiguous partition is Logical

If your system disk is initialized as MBR, there could be Primary and Logical partition on this disk. If the contiguous partition D is Logical, Windows Disk Management cannot extend C drive by either shrinking or deleting D. After deleting a Logical drive in Disk Management, you'll get Free space instead of Unallocated. Although this space is contiguous and on the right of C drive, Extend Volume is still disabled.

Extend volume disabled

There's no such issue if the contiguous partition D is Primary, however, you if you installed programs or Windows services in it, do not delete it to extend C drive.

What to do when unable to extend C drive in Windows 10/8/7

If you are unable to extend C drive in Windows 10/8/7 Disk Management because Unallocated space is non-adjacent. you just need to move Unallocated space next to C drive, then Extend Volume will be enabled.

How to fix the issue when unable to extend C drive volume in Windows 10/8/7:

  1. Download NIUBI Partition Editor, right click D: drive (the contiguous partition) and select "Resize/Move Volume", drag the middle towards right in the pop-up window, then Unallocated space is moved to the left.
  2. Right click C: drive and run "Resize/Move Volume" again, drag right border towards right to combine this Unallocated space.
  3. Click Apply on top left to take effect, done.

Follow the steps in the video.

Video guide

If D drive is Logical and you've deleted it in Disk Management, follow the steps to extend C drive:

  1. Create a new volume with the Free space that deleted from D in Disk Management.
  2. Right click this new volume in NIUBI Partition Editor and run "Resize/Move Volume", drag left border towards right in the pop-up window to make Unallocated space on the left.
  3. Follow step 2 above to add Unallocated space to C drive.

Other reasons why unable to extend data volume in Windows 10/8/7

In fact, both Shrink and Extend Volume functions support NTFS partition only, FAT32 and any other types of partitions cannot be shrunk or extended. To show you the truth, I formatted D drive from NTFS to FAT32. As you see, Extend Volume is disabled for D drive, although there's contiguous Unallocated space on the right.

Cannot extend partition

Solution 1: Run "Resize/Move Volume" for D drive in NIUBI, simply drag right border towards right to merge this Unallocated space. There's no difference to resize NTFS or FAT32 partition.

If you use a 2TB+ MBR disk, there's another possible reason why Disk Management is unable to extend volume in Windows 10/8/7. If you initialize a 4TB hard disk as MBR, you can only use 2TB space, the remaining space will be shown as Unallocated. When you right click this Unallocated space, all options are grayed out.

As you see in the screenshot, drive F is NTFS and there's contiguous Unallocated space on the right, but Extend Volume still doesn't work. To extend F drive, you must convert MBR disk to GPT first.

Extend Volume disabled

Solution 2: Right click the front of this disk and select "Convert to GPT Disk". After converting MBR disk to GPT, there's no longer 2TB restriction. You just need to follow the method above to extend partition with Unallocated space.

In Summary

When you are unable to extend C drive in Windows 10/8/7 Disk Management, find out the reason and follow the corresponding solution above. Besides resizing and moving partition, NIUBI Partition Editor helps you do many other operations such as merge, convert, copy, defrag, wipe, hide, scan partitions, etc. Better than other tools, it has unique 1 Second Rollback, Virtual Mode and Cancel-at-well technologies to protect system and data.

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