Is there any way to truly undo dcpromo? That is, a way that will restore all prior SAM accounts and passwords. Something less than a full drive backup?
A similar question (Will demoting a Windows Server 2003 Domain Controller reinstate local accounts?) asks if the demote command will automatically do this. This question asks if there is a way to pick up where it left off.
That is a one-way street. Once you've promoted you've overwritten the local security principles with new ones, and the same thing happens in reverse when you demote from Domain Controller. Windows does not keep an oops archive just in case you change your mind.