Add the logon screen of Windows XP
Press CTRL + ALT + DELETE on your keyboard
Enter in the username field
AdministratorLeave the password
BLANK dont enter anything
That should allow you to access your computer
NEXTClick Start
Control Panel
Click Users Accounts
At the bottom there is option that says "or pick an account to change"
Click the name of the user account that has a password on it/
You should have on the next page, a option to remove password