This hasn’t ever happened to me, but if you cannot remember the domain admin’s password, follow these steps to reset it.
Boot from install media and when it gets to the Windows install, select Next – Repair your computer – Troubleshoot – Command Prompt
cd c:\windows\system32 # if Windows isn’t on C drive, then type “wmic logicaldisk get caption,description,filesystem” to get the drive letter
ren Utilman.exe Utilman.exe.old
copy cmd.exe Utilman.exe
Reboot the server. Don’t boot to CD, let it boot from the hard drive. At the login screen, use the shortcut “Windows Key + U” to bring up admin cmd.
Now just type “net user administrator Password123” or whatever you want your password to be. Login and shut down the server. Boot from the install media again and get to the command prompt following step 1.
ren Utilman.exe.old Utilman.exe
- Exit and reboot the server. Take out the boot disk and boot normally. Done.
NOTE: You can do all this from within Windows by taking all the permissions of utilman.exe, but I prefer the above method.