a google search would help you.
are you able to log onto the box at all?
if you can log onto the box then consider a tool like Cain and Able.
if you can't there are various Linux live CDs that you can use to boot from a CD, read the SAM database and recover passwords.
Now, that's about as good as the information that comes from here can be, (I'm not saying I'm the authority on cracking passwords), I'm saying that you could have gotten that info from a google search, and that might help you form some better searches.
it's just that this isn't some kind of hacker forum, high level information is ok, but we don't want people giving detailed accounts of how to recover or steal passwords.
I'm not going to lock the thread.
but if anyone gets any more detailed, then their posts on the subject are likely to be removed.