Windows have the option to reset the admin pass with floppy ??? to reset the password in our time :
Start the windows or the server with the installation disk
At the first screen press SHIFT+F10 to get the CMD screen, then:
cd Windows\System32
ren Utilman.exe Utilman.exe.original
copy cmd.exe Utilman.exe
shutdown -r -t 0
Now when the server will reboot just press at the login screen The Windows key+U (Easy Of Access) now since we have change this file to cmd.exe you will get Command Prompt screen, Now type this to change the password to P@ssword123 For example :
net user Administrator P@ssword123
If the administrator account is disabled, you can this to enable account :
net user administrator /active:yes
Check to see if you can login with that password and reboot the server again to undo the changes you just made :
At the first screen press SHIFT+F10 to get the CMD screen, then:
cd Windows\System32
del Utilman.exe
ren Utilman.exe.original Utilman.exe
shutdown -r -t 0