Cannot extend C drive in Windows Server 2008

Updated on: November 16, 2019

This article introduces why cannot extend C drive in Windows Server 2008 with Diskpart or Disk Management, and what to do if cannot extend system partition.

Why can't extend C drive with Diskpart command

Diskpart is a command line tool that is integrated from Windows XP. It is very easy and fast, however it only supports NTFS partition. Most of system C drive is formatted with NTFS, then why many people feedback that they cannot extend C drive with Diskpart?

As we know, the size of a hard disk is fixed, therefore, before extending a partition there must be free Unallocated space. To get such space, you may either delete or shrink a partition. By 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 works, the syntax and the limitations.

Extend command limitation

To be short:

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

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

Why cannot extend C drive via Disk Management

Disk Management is the GUI version of Diskpart in some ways, it has same restriction while shrinking and extending partition.

  • Unallocated space can only be made on the right after shrinking.
  • 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 reason why cannot extend C drive in Windows Server 2008 Disk Management.

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

Extend greyed

In Disk Management, there's another probable reason.

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 deleted from Primary partition can't be extended to any Logical partition. Free space deleted from Logical partition can't be extended to any Primary partition.

Diskpart has no such restriction, Free space deleted from D can be extended to C drive.

Extend volume disabled

What to do if cannot extend system partition C

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. In that case, NIUBI can shrink it and make Unallocated space on the left directly.

How to fix can't extend system C drive in Windows Server 2008 R2:

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 middle position 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)

Video guide to fix cannot extend C: drive in Windows 2008 server:

Video guide

The steps are the same no matter drive D is NTFS or FAT32, Primary or Logical partition. There's also no difference if you use any types of hardware RAID arrays, or VMware/Hyper-V. Better than other tools, NIUBI Partition Editor has unique 1 Second Rollback, Virtual Mode and Cancel-at-well technologies to protect your system and data.