I wanted to copy a system disk to a VHD, but when AOMEI Partitioner goes into PreOS mode, it say Error 12, system has changed - obviously, it needs to mount VHD somehow!
We are so sorry forthis problem you encountered.
This problem is caused by Windows DeviceManager, when the system start the Device Manager may load your device one byone, and then record the number of your device, when you reboot if the number of device is not same as the record, it may cause the error code 12, so you'd better keep the same number of devices before your operation.
The most efficient solution is that do the operation in WindowsPreinstall Environment, therefore you need to create AOMEI Partition Assistant bootable CD and then boot from the CD to do the operation.
To create Partition Assistant bootable CD, please refer to this tutorial:
If you have any other question please feel free to let us know.
AOMEI SUPPORT TEAM