If you need to crack a Windows password, use this

[Trouble]

http://ophcrack.sourceforge.net/
Sourceforge page http://sourceforge.net/projects/ophcrack/

This is a legitimate tool. I just used this to get into a client's computer.

If you have the hash, you can type it in at this page http://www.objectif-securite.ch/en/products.php and they will crack it right then and there.