How to Reset Server 2012 Administrator Password

1- First, you’ll need to create a bootable Server 2012 disk on a flash drive.
2- Reboot your computer by using this flash drive.
3- When you see the initial Server 2012 setup screen, press Shift + F10 to open a Command Prompt. 

OR

From the Windows Setup menu, click "Next".

Select "Repair your computer".

Click on "Troubleshoot".

Under Advanced options, click "Command Prompt".

4- At the Command Prompt, Run the Following Commands

• C:   (If you cannot locate C:\Windows\System32\Utilman.exe then Windows has used another drive letter instead of C:\.)* See PS.
• cd Windows\System32
• ren Utilman.exe Utilman.exe.old
• copy cmd.exe Utilman.exe 

5- Close the command prompt.

6- Reboot the Server.

7- Wait for the login screen then press Windows Key + U at login screen.

8- At the command prompt run the following command to reset password to Password123.

• net user administrator Password123 

At this point, you have successfully reset the administrator password. Good work! 

Revert Changes 

For the last piece, you will revert the changes you made to rename cmd.exe to Utilman.exe by rebooting the server with the DVD\ISO again.

1- First, you’ll need to create a bootable Server 2012 disk on a flash drive. 
2- Reboot your computer by using this flash drive. 
3- When you see the initial Server 2012 setup screen, press Shift + F10 to open a Command Prompt. 


OR

From the Windows Setup menu, click "Next".

Select "Repair your computer".

Click on "Troubleshoot".

Under Advanced options, click "Command Prompt".

4- At the command prompt run the following commands to revert to the previous files.

• C:
• cd Windows\System32 
• del Utilman.exe 
• ren Utilman.exe.old Utilman.exe 

5- Restart Server

That is it! You have reset the domain admin password and can now access the machine.

I highly recommend you to check the user who change the password by going

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()* PS.
To determine what drive letters are in use on the server run this command.

wmic logicaldisk get caption,description,filesystem

Make note of the drive letters presented in the command prompt and search each drive until you find \Windows\System32\Utilman.exe

If Utilman.exe is located on another drive letter, substitute that letter for C:\ going forward.