1.First reboot Windows XP in safe mode by re-starting the computer and
pressing F8 repeated as the computer starts up.
2.Then (in safe mode) click Start and then click Run. In the open box
type “control userpasswords2” without the quotes – I have just used
quotes to differentiate what you have to type.
3.You will now have access to all the user accounts, including the
administrators account and will be able to reset the lost password.
4.Just click the administrators user account, and then click Reset
5.You will need to add a new password in the New password and the
Confirm new password boxes, and confirm by clicking OK.