Can't extend C

Windows Server 2008 can’t extend C drive volume

Windows Server 2008 added Extend Volume feature in Disk Management utility, but many people feedback that they cannot extend C drive after shrinking D. This page explains why you can’t extend C drive volume in Windows Server 2008 (R2) Disk Management, and show you easy method to solve this problem.

Can't extend C

Why can’t extend C drive

The built-in Extend Volume can help expand disk partition on the fly, but not all partitions can be extended. There are some limitations that cause you unable to extend C drive in Server 2008 Disk Management. In fact, Extend Volume only supports NTFS partition, however, this is not an issue for system C drive. Here I’ll introduce other 2 common reasons one by one.

Reason 1 No adjacent Unallocated space

To extend a disk partition, there must be Unallocated space. As its name, it is not allocated to any partitions. There are two ways to get Unallocated space in a hard disk: delete or shrink an allocated partition. By deleting volume, all disk space of this volume will be converted to Unallocated, all files in this volume will be deleted, too.

By shrinking a volume, only part of free space will be converted to Unallocated and all files keep intact. Obviously, this is the best idea, but:

  • Shrink Volume can only shrink a volume towards left and produce Unallocated space on the right side.
  • Extend Volume only works when there is adjacent Unallocate space on the right side.

To show you the result, I shrank drive D of my test server. As you see, 20GB Unallocated space is on the right side of D, so Extend Volume is disabled for C drive.

Can't extend C

The only way to enable Extend Volume for C drive in Disk Management is by deleting the adjacent drive D.

Extend Volume enabled

Caution Do NOT do this if you installed programs in drive D, or there is Windows service running from it.

Reason 2 Restriction between Primary and Logical partition

If your drive D is a Logical partition, you cannot extend C drive in Server 2008 DM even if you delete drive D.

Logical partition

Extend Volume disabled

To extend C drive in Disk Management, you have to right click the 50GB Free space and delete the Extended partition.

Delete Extend partition

Extend Volume enabled

Windows Server 2008 has been released for over 10 years, it formats disk as MBR by default when installing. MBR is the most common disk style originally, but because of some limitations it is been abandoned nowadays.

In a MBR disk, you can create maximum 4 Primary partitions or 3 Primary partitions plus an Extended partition. Extended partition works like a container and all Logical partitions must be created inside of it.

Logical partition

In my test server:

  • I cannot extend C drive by simply deleting Logical drive D.
  • I cannot extend drive D by deleting the Primary drive E.
  • If my drive E is also a Logical partition, to extend C drive in Disk Management, I have to delete the Logical partition D, then E, and then the entire Extended partition.

It is annoying, right? With server partition manager software, these problem can be solved easily.

What to do?

For reason 1, if you have shrank D and the Unallocated space is nonadjacent to C drive, you just need to move this space to the other side.

Steps to fix can’t extend C drive volume in Server 2008 DM:

Step 1 Download NIUBI Partition Editor, right click drive D and select “Resize/Move Volume”.

Move drive D

In the pop-up window, drag the middle position rightwards.

Drag to move

Unallocated space is moved to the other side (behind C drive).

Unallocated moved

Step 2 Right click drive C and select Resize/Move Volume again, drag the right border rightwards to combine the adjacent Unallocated space.

Extend C

C drive is extended to 50GB, click Apply on top left to execute, done.

C drive extended

For reason 2, you just need to follow Step 2 above to combine the adjacent free space.


  • This program is designed to work in its own virtual mode, so real disk partitions won’t be changed until click Apply to confirm.
  • The pending operations (at bottom left) marked as Check can be done in desktop without task interruption or server rebooting.

In Summary

When you cannot extend C drive volume in Windows Server 2008 (R2) Disk Management because of nonadjacent Unallocated space, run NIUBI Partition Editor and drag the middle position to move Unallocated space. If you can’t extend C drive because of the restriction between Primary and Logical partition, simply drag the border towards other side to combine the Free or Unallocated space.