Extend C: when the recovery partition is in the way

After cloning to a larger disk, the extra space often ends up at the end of the disk, behind the recovery partition. Windows only extends C: into the space directly after it: “Extend Volume” stays greyed out.

Why it is blocked

A Windows 10 or 11 disk in GPT holds, in order: the boot partition (EFI), a reserved partition, C:, then the Windows recovery partition (WinRE). A tool that copies the partitions in the same order leaves the extra space after the recovery partition. But Windows, like diskpart, can only extend a partition into free space that starts right after it.

On a PC upgraded from an older version of Windows, there are sometimes two recovery partitions: a small one at the start of the disk, often empty, and the one Windows really uses, after C:.

The manual method

It follows the procedure Microsoft publishes for enlarging the recovery partition (article KB5028997): remove the recovery partition, extend C:, then recreate the recovery partition at the end of the disk. Back up the customer’s data first. In a Command Prompt run as administrator:

reagentc /info: note the disk and the partition of the recovery environment.
reagentc /disable: Windows keeps its recovery image on C:, where reagentc /enable will pick it up again.
In diskpart, delete the recovery partition:
diskpart
list disk
select disk 0
list partition
select partition N
delete partition override
N is the number of the recovery partition. Check it twice: it is the one of type “Recovery”, after C:.
Still in diskpart, select C:, extend it over all the free space, then give back 1 GB at the end of the disk for the new recovery partition:
select partition N
extend
shrink desired=1024 minimum=1024
Here, N is the number of the Windows partition (C:).
Recreate the recovery partition. On a GPT disk:
create partition primary id=de94bba4-06d1-4d40-a16a-bfd50179d6ac
gpt attributes=0x8000000000000001
format quick fs=ntfs label="Windows RE tools"
On an MBR disk:
create partition primary id=27
format quick fs=ntfs label="Windows RE tools"
set id=27
exit, then reagentc /enable, and check with reagentc /info that the recovery environment is enabled, on the new partition.

The disk is GPT if list disk shows an asterisk in the “Gpt” column. One gigabyte is usually enough: Microsoft asks for the partition to keep 250 MB free on top of the image, for its updates.

With MBI Clone

The problem does not arise: MBI Clone rebuilds the new disk instead of copying the old layout, and places the recovery partition at the end of the disk. When cloning to a larger disk, C: is extended during the clone.

The recovery partition is enlarged when the source image requires it: the size of the image, plus the 250 MB of free space that Microsoft asks for.
Only one recovery partition is rebuilt: the one Windows uses. A duplicate or empty partition is not carried over, and MBI Clone says so.
The recovery environment is turned back on the first time an administrator signs in on the clone, and the result is checked.

Pitfalls

The wrong partition number: delete partition override deletes any partition, without asking. Read list partition again before each deletion.
Forgetting reagentc /enable: the PC no longer has a recovery environment, so Startup Repair and Reset this PC are no longer available from the Troubleshoot menu.
A manufacturer’s factory restore: this is not the same partition as the Windows one. Do not delete it without the customer’s agreement.

Common questions

Can I simply delete the recovery partition?

The PC boots, but it has no recovery environment until reagentc /enable has been run again. The method above puts it back properly, on a partition at the end of the disk.

Why is “Extend Volume” greyed out when there is free space?

Because the free space is not right after C:. Windows does not jump over another partition.

Do I need paid partitioning software?

No. The commands above are Windows commands, published by Microsoft.