[Solved] Cannot extend C drive on Windows Server 2022/2025

by John, Updated on: October 10, 2024

Low disk space is common issue in both Windows Server 2022 and 2025. When C drive is getting full, it can't be better if you can extend it without wasting a long time to recreate partitions and restore everything from backup. There's "extend volume" function in native Disk Management to help extend partition without losing data. However, many people feedback that they cannot extend C drive in Server 2022/2025 via Disk Management, because "extend volume" option is grayed out. This article introduces why Disk Management is unable to extend C drive in Windows Server 2022/2025 and how to solve this problem easily.

Can't extend C drive

Why inbuilt tool cannot extend C drive in Windows Server 2022/2025

First of all, you should know that Disk Management can only shrink and extend NTFS partitions, any other types of partitions (except RAW) are not supported. System partition C is formatted with NTFS by default. Therefore, this is not an issue.

There are 3 reasons why Disk Management is unable to extend C drive in Server 2022/2025:

  1. No adjacent unallocated space on the right
  2. The adjacent partition is logical
  3. 2TB restriction on MBR disk

I'll explain the reasons one by one.

1. No adjacent unallocated space on the right

To extend a partition in Server 2022/2025 with either Disk Management or diskpart command tool, there must be contiguous unallocated space on the right of this partition. For example: if you shrink D drive (must be NTFS) with either Windows inbuilt tool, you'll get unallocated space on the right of D drive. This unallocated space is on the left of E drive and is nonadjacent to C drive. Therefore, both partitions can't be extended via Disk Management or diskpart.

Disk Management

In some servers, there's a Recovery, EFI or OEM partition next to C drive. In that case, you can't get adjacent unallocated space in any way with Windows native tool.

2. The adjacent partition is logical

Some people tried to delete the adjacent partition D, but they still cannot extend C drive on Server 2022/2025. If you have the same problem, check if D drive is logical. In Windows Disk Management, "Free" space that deleted from a logical drive can't be extended to any primary partition. "Unallocated" space that shrunk from a primary partition can't be extended to any logical drive. Because C drive is primary partition in most cases, if the adjacent D drive is logical, Disk Management cannot extend C drive even after deleting D.

Cannot extend C drive

As you see the screenshot in my test server. The adjacent D drive is logical, it is changed to "Free" space after deleting it. "Extend volume" is still disabled for C drive.

3. 2TB restriction on MBR disk

If your system disk is MBR, there's another possible reason why you can't extend C drive for Server 2022/2025 with Disk Management. The maximum partition size on MBR disk is 2TB. If your system disk is 3TB, 1TB space will be shown as unallocated. This space can't be extended to other volume or used to create new volume. Few people encounter this issue because few people use 2TB+ MBR disk for operating system.

What to do when you are unable to extend C drive in Server 2022

Method 1 - move partition

If you've shrunk D drive and got unallocated space, you should run NIUBI Partition Editor to move D: drive to the right and make unallocated space next to C drive.

Steps when you can't extend C drive in Windows Server 2022/2025:

  1. Download NIUBI Partition Editor, right click D: drive and select "Resize/Move Volume", drag middle of D drive towards right in the pop-up window, then unallocated space will be moved to the left.
  2. Right click C: drive and run "Resize/Move Volume", drag right border towards right to combine this unallocated space.
  3. Click "Apply" on top left to take effect.

If there's a Recovery, EFI, OEM or other partition in the middle of C and D drive, you should continue to move these partitions to the right. Only after you move unallocated space next to C drive, you can extend C drive with this space.

Watch the video how to operate:

Move partition

Method 2 - resize partition with NPE

If you have not shrunk any partition to get unallocated space, run NIUBI Partition Editor to shrink the adjacent partition. To do this, right click the adjacent partition and select "Resize/Move Volume", drag left border towards right in the pop-up window, then unallocated space will be made on the left.

If you deleted logical partition D and cannot extend C drive in Server 2022/2025, follow the steps:

  1. Right click the "Free" space in Windows Disk Management and select "New Simple Volume".
  2. Run NIUBI Partition Editor to shrink this new partition and make unallocated space on the left.
  3. Extend C drive with this adjacent unallocated space.

Method 3 - convert MBR to GPT

When you cannot extend C drive in Windows server beyond 2TB, convert MBR to GPT. Windows Server 2022 and 2025 has MBR2GPT command to help convert system disk from MBR to GPT without losing data. If you want to convert a data only disk to GPT, NIUBI Partition Editor can help you.

Besides shrinking, extending, moving partition and converting disk partition type in Windows Server 2022/2025 and previous Server 2019/2016/2012/2008/2003, NIUBI Partition Editor helps you do many other disk partition management operations.

Download

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