If you forgot your password of your windows XP here is a simple solution.
1. Restart you computer
2.When booting, press F8 and select "Safe Mode"
3.After getting to the user menu. Click on a user and this time it will not ask you for a password
4.Go to Start>Run and type CMD .
5.At command prompt type in cd C:WindowsSystem32, (Where C put your system's HD letter,I am assuming C is your System/Windows Drive)
6.For safety purposes first make a backup of your Logon.Scr file.. You can do this by typing in Copy Logon.scr Logon.bak
7.Then type copy CMD.EXE Logon.scr
8.Then type this command, I will assume that you want to set Administrator's password to NewPass
9.Now, type this in net user administrator NewPass
10. You will get a message saying that it was successful, this means Administrator's new password is NewPass
11. Restart the PC and you will login as Administrator (or whatever you chose to reset) with your chosen password.