Step 1: Reboot your server, and with F8 key, go to Recovery
Step 2: Select “troubleshoot” option.
Step 3: Select “command prompt”.
Step 4: Inside CMD please type:
c:
cd Windows\System32
move utilman.exe utilman.exe.bak
copy cmd.exe utilman.exe
net user administrator /active:yes
shutdown -r -t 0
Step 5: After server reboot, on the home login screen, please press the Win+U combination. Inside CMD window, please type:
net user Administrator your-new-password
exit
Step 6: Your password has been reset. However, you need to rollback your changes with utilman.exe.
Just reboot your server, and repeat this guide. Inside CMD window in Windows Recovery mode, please type:
c:
cd Windows\System32
del utilman.exe ren utilman.exe.bak utilman.exe
shutdown -r -t 0