There are hundreds of applications that can break the password, but unless you *need* to break it, I'd suggest either bypassing it or resetting it.


Password reset:
http://pogostick.net/~pnh/ntpasswd/


Password bypass:
http://www.thelead82.com/kon-boot/

Passsword Recovery:
http://www.oxid.it/cain.html
http://www.openwall.com/john/
http://ophcrack.sourceforge.net/