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:

1. Boot from Microsoft Windows Server 2012 installation DVD / ISO Image.
2. From Windows Setup menu, click Next > Repair your computer > Troubleshoot > Command Prompt.
3. Run following commands:

   d:
   cd windows\system32
   ren Utilman.exe Utilman.exe.old
   copy cmd.exe Utilman.exe

4. Close command prompt and click Continue.
5. After server reboot and present the logon screen, click Windows Key + U to open command prompt.
6. Type following command:

   net user administrator Password123

   This will set the Administrator password to Password123 (case sensitive).

Cleanup Steps:

1. Restart server and boot from Microsoft Windows Server 2012 installation DVD / ISO Image.
2. From the Windows Setup menu, click Next > Repair your computer > Troubleshoot > Command Prompt.
3. Run following commands:

   d:
   cd windows\system32
   ren utilman.exe utilman.exe.new
   copy utilman.exe.old utilman.exe

4. Close the command prompt and click Continue.

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

1. Boot from Microsoft Windows Server 2008 installation DVD / ISO Image.
2. From the Install Windows menu, click Next > Repair your computer.
3. In the System Recovery Options, select the Operating System instance that you wish to repair and click Next > Command Prompt.
4. Run following commands:

   c:
   cd windows\system32
   ren Utilman.exe Utilman.exe.old
   copy cmd.exe Utilman.exe

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

   net user administrator Password12

   This will set the Administrator password to Password12 (case sensitive).

Cleanup Steps:

1. Delete the newly created Utilman.exe from C:\Windows\System32.
2. Rename Utilman.exe.old back to Utilman.exe.

Alternative: Offline NT Password & Registry Editor