Please Remember, it is for XP.
This is the easiest method.
When the system requests for password, Short it down by pressing down the power button.
Turn the computer on again.
but just before it starts to boot, press F8 on your keyboard.
The computer will request from you the mode in which you want it to boot.
Select Safe Mode.........
After this the computer will boot in safe mode (the only thing you see on your screen is my computer, recycle bin etc.)
Now open control pannel and go to user account.
Change the password to your choice, or rather remove it completely.
YOu can now reboot your system since you now have the new password.