[Solved] How to Reset Administrator Password in Windows Server 2008 R2 and 2012 R2

To reset the Administrator password on Windows Server 2012 R2, perform the following steps:

Step 1: Boot from Microsoft Windows Server 2012 installation DVD / ISO Image.

Step 2: From Windows Setup menu, click Next > Repair your computer > Troubleshoot > Command Prompt.

Step 3: Run following commands:
d:
cd windows\system32
ren Utilman.exe Utilman.exe.old
copy cmd.exe Utilman.exe

Step 4: Close command prompt and click Continue.

Step 5: After server reboot and present the logon screen, click Windows Key + U to open command prompt.

Step 6: Type following command:
net user administrator Password123
This will set the Administrator password to Password123 (case sensitive).

Cleanup Steps:

Step 1: Restart server and boot from Microsoft Windows Server 2012 installation DVD / ISO Image.

Step 2: From the Windows Setup menu, click Next > Repair your computer > Troubleshoot > Command Prompt.

Step 3: Run following commands:
d:
cd windows\system32
ren utilman.exe utilman.exe.new
copy utilman.exe.old utilman.exe

Step 4: Close the command prompt and click Continue.

To reset the Administrator password on Windows Server 2008 R2, perform the following steps:

Step 1: Boot from Microsoft Windows Server 2008 installation DVD / ISO Image.

Step 2: From the Install Windows menu, click Next > Repair your computer.

Step 3: In the System Recovery Options, select the Operating System instance that you wish to repair and click Next > Command Prompt.

Step 4: Run following commands:
c:
cd windows\system32
ren Utilman.exe Utilman.exe.old
copy cmd.exe Utilman.exe

Step 5: After server reboot and present the logon screen, press Windows Key + U to open command prompt.

Step 6: Enter following command:
net user administrator Password12
This will set the Administrator password to Password12 (case sensitive).

Cleanup Steps:

Step 1: Delete the newly created Utilman.exe from C:\Windows\System32.

Step 2: Rename Utilman.exe.old back to Utilman.exe.

Alternative: Offline NT Password & Registry Editor