Cannot Extend C Drive in Windows Server 2008 R2 - How to Fix

by Allen, Updated on: August 24, 2022

Better than previous Server 2003, Windows Server 2008 has new "Extend Volume" function in Disk Management to help extend NTFS partition without losing data. When system C: drive is getting full, many people try to extend partition with this native tool but failed. When right click C drive, they found that "Extend Volume" option is grayed out. In this article, I'll introduce why you cannot extend C drive in Windows Server 2008 (R2) with Disk Management or another diskpart command tool, and how to solve this problem easily.

Why can't extend C drive in Server 2008 R2 with Diskpart command

Diskpart is a command line tool that is integrated from Windows XP. It has the command to shrink and extend partition, however it only supports NTFS partition. Most of system C drive is formatted with NTFS, then why many people still feedback that they cannot extend C drive with Diskpart in Server 2008 R2?

As we know, the size of a physical disk is fixed, a 500GB disk can't be decreased to 250GB or increased to 1TB. You can change size of a partition but you cannot resize a physical disk. Therefore, before extending a partition there must be "Unallocated" space on the same disk. To get Unallocated space, you may either delete or shrink a partition. When shrinking a volume, all files in it keep intact, so it's better than deleting.

I did shrink drive D with 20GB, but when I extend C drive, I receive error message - The size of the extent is less than the minimum.

Diskpart extend error

I then deleted drive D and retry extending, this time diskpart reports C drive is successfully extended.

Extend done

Type help extend in diskpart command prompt, you'll see how extend command works, the syntax and the limitations.

Extend command limitation

To be short:

System partition C is NTFS and the Unallocated space that shrunk from D is also on the same disk. But, this Unallocated space is on the right of D after shrinking, so it cannot be extended to the nonadjacent C drive. This is the reason why you can't extend C: drive in Server 2008 (R2) with diskpart.

Do not delete D: drive if there are programs or Windows services running from it.

Why cannot extend C drive in Windows Server 2008 with Disk Management

Disk Management has graphic interface and it is easier to use. However, it has same restriction with diskpart command while shrinking and extending partition.

  • Unallocated space can only be made on the right after shrinking partition.
  • Unallocated space can only be combined to the left contiguous partition.

Therefore, Extend Volume is disabled for C: and E drive after shrinking D.

This is the most common reason why you cannot extend C drive in Windows Server 2008 R2 with Disk Management.

If Disk Management can make Unallocated space on the left or move partition to the right or left, there is no such issue.

Extend greyed

Unlike diskpart command, if the right adjacent drive D is Logical, Disk Management still cannot extend C drive after deleting D.

In Server 2008 Disk Management, Unallocated space that deleted from Primary partition can't be extended to any Logical partition. "Free" space that deleted from Logical drive can't be extended to any Primary partition.

This is another common reason why you can't extend C drive in Server 2008 (R2) with Disk Management.

To convert this "Free" space to "Unallocated", you must delete all other Logical drives and then delete the entire Extended partition. Obviously, it is bad idea. 

Extend volume disabled

What to do when you are unable to extend C drive in Server 2008

It is easy to solve this problem with NIUBI Partition Editor. If you have shrunk D or other volume, NIUBI can move Unallocated space behind C drive. If the contiguous D drive is FAT32, neither Diskpart command nor Disk Management can shrink it. But NIUBI can shrink it and make Unallocated space on the left, then C drive cann be extended without moving partition D.

Steps when you cannot extend C drive in Windows Server 2008 R2 after shrinking D (or E):

Download NIUBI Partition Editor and you'll see the main window with disk partition structure and other information. There is 20GB Unallocated space in Disk 0 that is shrunk from drive D.

NIUBI Partition Editor

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

Move drive D

Then Unallocated space is moved to the left.

Move Unallocated space

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 Unallocated space is combined to C: drive.

Move Unallocated space

Step 3: Click Apply on top left to execute. (All operations before this step only work in virtual mode)

Watch the video guide how to operate:

Video guide

If there's adjacent Unallocated space on the right, but you still cannot extend C drive, check the size of C drive and if this disk is MBR. You can only use 2TB space on MBR disk no matter how big it is. If your system disk is MBR, follow the steps to convert MBR to GPT. After that, you can extend C drive easily.  

Besides shrinking, moving, extending partition and convert disk type, NIUBI Partition Editor helps you do many other disk partition management operations. Better than other tools, it has unique 1 Second Rollback, Virtual Mode and Cancel-at-will technologies to protect your system and data.