Method 1

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.

Method 2

1.Put your hard disk of your computer in any other pc .
Step 2.Boot that computer and use your hard disk as a secondary hard disk (D'nt boot as primary hard disk ).
Step 3.Then open that drive in which the victimís window(or your window) is installed.
Step 4.Go to location windows->system32->config
Step 5.And delete SAM.exe and SAM.log
Step 6.Now remove hard disk and put in your computer.
Step 7.And boot your computer :-)