When trying to enable the Windows RE partition from a Command Prompt by running reagentc.exe /enable, you may get error 3B3C.
In reality, the recovery partition itself is not the cause here. The real issue is the attributes of the EFI partition. The EFI partition must carry a specific flag so that reagentc can do its job without errors.
In diskpart, once you have selected the EFI partition, you can use detail partition to view that partition’s parameters.
An EFI partition must always have the following ID (the “Type” parameter):
c12a7328-f81f-11d2-ba4b-00a0c93ec93b
If it has any other ID — especially the standard partition ID
ebd0a0a2-b9e5-4433-87c0-68b6b72699c7 — you need to correct the EFI partition type with the following command:
set id=c12a7328-f81f-11d2-ba4b-00a0c93ec93b
No restart is required afterward. The command reagentc.exe /enable should then complete without errors.
Another related issue:
If the activation attempt reports a missing recovery image, you need to extract winre.wim from a Windows ISO and place it in the folder C:\Windows\System32\Recovery. After that, the command should run successfully and correctly populate the RE partition with the data from the recovery image.
The install.wim file is located in the Sources folder of the Windows ISO. The required file can then be found inside install.wim or install.esd under Windows\System32\Recovery.
