Boot to safe mode and administrator will be listed as available to login. If you are lucky it won't have password set. Once in create a new user through control panel as an administrator and when reboot, log in with new user. While there should be able to delete the other users passwords as well.
Boot your system to save mode by continuously pressing F8 on the keyboard.the system will boot to window xp on save mode.then click go to control panel,click on user account,click on Administrator,click on the name that was locked,locate and click on remove password.restart the system.the problem is solved.Goodluck