Reset Windows Server 2008 Domain Administrator Password

Boot onto DVD of Windows Server 2008
Choose “Repair your computer”
Launch cmd
Go to c:\windows\system32
Rename Utilman.exe to Utilman.exe.bak
Copy cmd.exe to Utilman.exe
Reboot on Windows
Do the keyboard shortcut Windows + U when on the logon screen
net user administrator Newpass123 inside the cmd
log on with the domain admin account and this new pass
change the password to remember it if needed
Reboot on the DVD to put back the original Utilman.exe

Thx to mathieu chateau