In this post, you’ll learn more about the Error ERROR_VOLMGR_EXTENT_ALREADY_USED – 0xC038001A that is returned when working with the COM-based APIs in Win32
Win32 COM Error
ERROR_VOLMGR_EXTENT_ALREADY_USED – 0xC038001A
Win32 COM Error Error Description
The specified extent is already used by other volumes.