This is the software I use, burn the iso to cd, it is a bootable linux disk that will read the windows registry, and allow you to change/delete a password. I would suggest making the password blank to delete it, then when you reboot it should have no password, then you can re-assign it.
http://home.eunet.no/~pnordahl/ntpasswd/bootdisk.html
I have used this on windows 2000 pro, windows2000 server, and Windows XP