I would like to cover this topic since it is essential and important for the system administrator.
The system administrator should aware that the lost password can be happened at anytime if we manage bulk servers especially the standalone server or non join domain to active directory.
So the step is straight forward and simple.
Step 1: Boot the System using Bootable DVD of Windows Server 2012
Boot the server or your system and insert the Bootable DVD/CD of Windows Server 2012 / R2. Click Next button.
then, click the ‘Repair your computer’.
Step 2: Run the Command Prompt from Advanced Option.
At the option menu, click the ‘TroubleShoot’ menu.
At the Advanced Option, choose Command Prompt.
At the Command Prompt,
Step 3: Rename and Copy UtilMan.exe
Rename the old utilman.exe to utilman.exe.old
Copy the utilman.exe by running the command
“Copy cmd.exe utilman.exe”
after that, close and reboot it.
Step 4: Boot and Press Windows button Keyboard + U at Logon Screen.
While Rebooting the server and let the Windows Logo Appear. After that press the Windows button at your keyboard plus pressing the U. + U
Step 5: Reset the administrator password using Net User Command Prompt.
When you press windows key + U button, the command prompt will be appeared.
then, type the command below
Net User Administrator YourPassw0rd
Finally,reboot your system and log on using the new password.