if you can login on another account as admin, then maybe ;
To log on to a computer as the administrator to reset a password, try the following steps.
1. Log on as an administrator.
a. Restart the computer.
b. Press CTRL+ALT+DELETE two times, and then type the name of the administrator user account.
c. In the Password box, type the administrator password, and then click OK.
Note If the administrator password is set to a blank password, do not type a password before you click OK.
2. Reset the password.
a. Click Start, and then click Run.
b. Type control userpasswords2, and then click OK.
c. On the Users tab, click the name of the user account that you want to reset the password for, and then click Reset Password.
d. Type a new password in the New password box, and then type the password again in the Confirm new password box, and then click OK.
e. Restart the computer, and then try to log on to Windows XP again.
Failing that,you can get rid of the password using offline NT password Registry editor
Though i recommend printing the walkthrough document...i have used this before and it does work,though some time ago click here