Why is “Extend Volume” Grayed out in Disk Management

When you try to extend a volume in Disk Management, the Extend Volume option may be grayed out even though there is unallocated space on the disk.

Cause

The Extend option is grayed out because a partition (i.e., Recovery) appears between C: and the Unallocated space. Disk Management doesn’t let you extend a partition if the free space is not adjacent to the volume. Importantly, the free space must be on the immediate right side of the drive you plan to extend.

Resolution

Given the above situation, here are your options to extend the volume:

Option 1

As the “Recovery” partition appears between C: and the unallocated space, disable Windows Recovery Environment using ReAgentC.exe.

Then, use Diskpart to delete the Recovery partition. Extend C: by occupying the unallocated space (minus 750 MB for the Recovery partition). Then create a Recovery partition and the end of the disk and re-enable WinRE.

Option 2

Use a third-party tool like NIUBI Partition Editor or AOMEI to extend C into the non-contiguous unallocated space.