for windows you should boot into safe mode by pressing F8 during the boot screen on your computer (before the windows OS loads) from there go to control panel and change your password to whatever you like
That only works if there is an admin account that isn't passworded in the selection screen,so if you don't have that option you need a password reset disk,you'll need to search the net there is one but i can't remember the name of it, it's base is linux & is able to reset your pass to none & it's free in that no money
this is the bootcd I've used to reset the admin password on windows xp, it works eveytime. It's free. http://home.eunet.no/~pnordahl/ntpasswd/