Enable Windows Directory Services Restore Mode (DSRM)

Boot with Windows Boot CD/ISO and when you see Install now, click on Repair your computer → Troubleshoot → Command Prompt.

• Find the Windows volume (usually C:):

  • dir C:\Windows to confirm it exists.​

• Tell Windows to boot into Directory Services Restore Mode (DSRM) on the next boot:

  • bcdedit /set {default} safeboot dsrepair​

Close the Command Prompt and reboot the machine. On next boot, the DC should start in Directory Services Restore Mode. Log on using the DSRM password you set when promoting the DC (local, not domain). Enter the username as .\\Administrator.

Once you’ve fixed whatever issues and want normal startup again:

• From an elevated Command Prompt inside Windows on that DC, run:

  • bcdedit /deletevalue {default} safeboot​

Then reboot; it will go back to normal DC mode.