How to Extend the C: Drive When a Recovery Partition Blocks the Newly Added Space

Overview

In some Softdrive Windows virtual machines (oVirt), administrators may expand disk storage at the hypervisor level but then find that the C: drive cannot be extended in Windows. This happens when a Windows Recovery partition is located between the C: partition and the newly added Unallocated space, which prevents Windows Disk Management from extending the volume.

Common Causes

• A template that had this disk arrange.
• The disk layout appears similar to:
  [ EFI ] [ C: ] [ Recovery ] [ Unallocated ]
  Since the Unallocated space is not immediately to the right of C:, Windows disables Extend Volume.
• Windows Disk Management cannot move partitions, so it cannot “shift” the Recovery partition out of the way.

Troubleshooting

Symptoms

• The disk expansion was completed successfully, and the added space appears as Unallocated.
• Extend Volume is grayed out on the C: drive in Disk Management.
• A small Healthy (Recovery Partition) sits between C: and the unallocated space.

Important Notes (Before You Proceed)

• Recommended: Take a VM snapshot before making partition changes.
• You must be logged in as a local Administrator.
• If BitLocker is enabled on C:, suspend protection first:
  manage-bde -protectors -disable C:

Resolution Option A (Recommended): Remove Recovery Partition, Extend C:

This is the most common approach for managed VMs where Windows Recovery (WinRE) is not heavily used.

Step 1: Disable Windows Recovery (WinRE)

Open Command Prompt as Administrator and run:

reagentc /disable

Verify WinRE is disabled:

reagentc /info

Expected result:
Windows RE status: Disabled

Step 2: Delete the Recovery Partition (DiskPart)

Disk Management usually cannot remove protected recovery partitions. Use DiskPart:

diskpart
list disk
select disk 0
list partition

Identify the partition labeled Recovery (often ~500–600 MB). Then run:

select partition <number>
delete partition override
exit

Step 3: Extend the C: Drive

1. Open Disk Management.
2. Right-click C: and select Extend Volume.
3. Use the available unallocated space and complete the wizard.

Optional: Recreate the Recovery Partition Later

The Recovery partition (WinRE) is not required for normal Windows operation, especially in managed virtual desktop environments. However, if you want to recreate it later, you can do so after extending C:.

High-Level Steps (Optional)

1. Shrink C: by 600–1024 MB to create unallocated space at the end of the disk.
2. Create a new small NTFS partition (e.g., 1024 MB) in that space.
3. Enable WinRE again so Windows registers a recovery environment:

reagentc /enable
reagentc /info

If WinRE enables successfully, the recovery environment is restored. You may remove the temporary drive letter afterward if you assigned one.

Support Details

• If reagentc /enable fails, confirm the system has enough free space (600–1024 MB) for a recovery partition and retry.
• If BitLocker was suspended earlier, re-enable protectors after completing changes:
  manage-bde -protectors -enable C:
• Best practice to avoid this in future deployments: right-size OS disks at provisioning time and/or use standardized templates that place the Recovery partition before C:, or use a separate data disk for growth.

Summary

The disk expansion at the hypervisor level is successful, but Windows can only extend partitions into adjacent unallocated space. When a Recovery partition sits between C: and the unallocated space, you must remove (or relocate via third-party tooling) the Recovery partition before extending C:.