First method :-
Boot up with DOS and delete the sam.exe and sam.log files from Windows\system32\config in your hard drive.
Now when you boot up in NT the password on your built-in administrator account which will be blank (i.e No password).
This solution works only if your hard drive is FAT kind.
Second method :-
Put your hard disk of your computer in any other pc .
Boot that computer and use your hard disk as a secondary hard disk (D’nt boot as primary hard disk ).
Then open that drive in which the victim’s window(or your window) is installed.
Go to location windows->system32->config
> And delete SAM.exe and SAM.log
Now remove hard disk and put in your computer.
And boot your computer……