Why Sysprep is important …
Trying to be time and space efficient in a reproduction for a colleague I tried to set up a multi domain forest for some SSO issues a customer is experiencing.
The promote of the first domain controller went fairly smooth but 2 others experienced some issues during the promote process.
Simply clicking yes just brought up the same screen a few seconds later. As I had to change the computer name of that particular VM which I wanted to promote due to another error I tried to find out if an orphaned child domain was present due to the earlier failure but neither ldifde nor ntdsutil could find any existing child domains.
Clicking no in the installation wizard gave the clue I needed, I had used a duplicate SID for a computer.
That was when I remember that to save some space on the SSD I had used the linked clone feature of VMware Workstation. A quick check with PsGetsid from the sysinternals suite confirmed the issue.
After sysprepping the systems I could finally create the desired forest structure required by my colleague.