[art_arev]

Try this:
First reboot Windows XP in safe mode by re-starting the computer and pressing F8 repeated as the computer starts up. 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. You will now have access to all the user accounts, including the administrators account and will be able to reset the lost password. •Just click the administrators user account, and then click Reset Password.
•You will need to add a new password in the New password and the Confirm new password boxes, and confirm by clicking OK.
•All done, you have recovered the lost administrators password!

Or this:
This will only work if you have Windows XP Professional, and you can login with an account. Right click on My Computer and select Manage. Then select Local User and Groups ““> Users. Right click on your username and select Set Password. Follow the prompts and set yourself a new password.

Or this:
If the above steps have failed so far, you can try and boot into Safe Mode. To do this, press F8 while your computer is booting. Once in safe mode, you can try going into the control panel and reset your password. If you can’t, you can try and open up a Command Prompt by opening Run and typing cmd. Enter net user [username] [enternewpassword]. For example, If I want to change my account which is Jack to password abcde, I would type in net user jack abcde and press enter. Your password should now be changed.