See some links at the bottom of this page for hints on where to find such tools, but I can tell you right away that Google might be a better choice for you. It even works if no passwords at all are known for the machine (as long as you have your Windows XP CD, you can get back into your system using a simple but effective method made possible by a little known access hole in Windows XP. If the computer or online system supports the pass phrase directly. Your passwords are the keys you use to access personal information that you've stored on your computer and in your online accounts. And it’s free - I mention that because you can pay two hundred dollars for an emergency download of Winternals ERD with Locksmith which is a utility for unlocking.