‘The volume you have selected may not be extended’ error when attempting a volume extension using Diskpart

I encountered this problem trying to resize the system drive of a virtual machine. Normally I add the extra space using the vSphere client then power down the VM before adding the virtual disk as a secondary disk on another Windows 2003 VM. There I can usually run Diskpart and safely extend it, detach as a secondary drive and power up the original VM with it’s now extended system drive.

In this instance I received the error:
The volume you have selected may not be extended.
Please select another volume and try again.

After a liitle research and reading I found this which pointed me in the right direction:


I downloaded fsextend and saved into C:WindowsSystem32 and then whilst still using the Diskpart utility, ran the command:
extend filesystem

But I still received the error. I was about to run the fsextend utility directly as the only syntax it requires is fsextend (drive letter) when I realised that I would need a drive letter for the volume I was attempting to extend (I don’t normally assign a letter – the volume usually extends without)

I assigned a drive letter and whilst still in the same session of Diskpart ran extend filesystem again but this time it was successful..

I’m not sure whether simply assigning a drive letter resolved the issue or whether fsextend helped in some way.

I later found out that from Windows 2003 SP2 the Diskpart utility has the extra and originally undocumented filesystem command included natively within the utility. In theory you should not need the fsextend utility above if running the latest Windows 2003 SP2 and it may be worth assigning a drive letter temporarily to see if this resolves the extending issue in the first instance.