You're dealing with Windows XP, right? Well if that's the case then there's a much easier way to get into any of the accounts. I don't know how to crack the passwords like you asked but (assuming the previous owner is just some ignorant luser) an easier way is to just bypass them. First I would recommend that you get the XP disk somehow and just re-install windows bc then you can customize it however you like, but if you would rather just access the system then here goes. I live in a dorm, so we have a lot of fun messing with each other's computers and being able to bypass a Windows XP password is a must-have skill if you're going to have any fun When the computer is booting up you can use the "boot keys" which means you hit a function key (like f5 or f8) when the computer is just starting up to do something before the computer goes into windows. It is much easier to manipulate the other versions of windows, but on XP you can hit F8 repeatedly as soon as the power comes on and you'll get a menu asking what you want to do. Select "boot into safe mode" and when the welcome screen somes up there's a new account labeled "Administrator". From this account you can change (or remove) the passwords of other accounts without having to know the password! This can be disabled, but it worked on all the computers I've tried it on to date. If I missed something, please don't flame me. Thanks
-keezel