How to Change a Windows XP Password

1rd Method:
Try following trick which is actually a loophole in Windows XP Setup and a big security hole:
A. Boot using Windows XP Setup CD and follow the instruction like Accepting EULA, etc.
B. When it asks to repair your existing Windows installation, accept it and press "R" to run the repair.
C. Setup will start repairing your Windows and will start copying files, etc.
D. After a few minutes setup will restart your system and when it restarts don't press any key when it shows "Press any key to continue..." otherwise Setup will start from the beginning. Don't press any key and setup will resume where it left.
E. Now it'll start doing other tasks and will show a small progressbar with a few details in left side.
F. Look carefully at the details and when it shows "Installing devices", press <Shift>+F10 keys in your keyboard.
G. It'll open a Command Prompt window. Now type nusrmgr.cpl and press <Enter>.
H. It'll open the same "User Accounts" window which you see in Control Panel.
I. Now you can remove or reset any account password without any problem.
2th Method:
There are many 3rd party utilities which claim to recover forgotten Windows password: The programs that I recommend are the Windows Password Key 8.0 and Windows Password Recovery 6.0 . They are a very quick and useful utilities for resetting passwords. They not only supports XP, 2000, and NT, I have personally tested it with Vista Home Premium and Ultimate. They works perfectly to reset any local user account to a blank password.
Just an easy to use bootable CD/DVD . They can also be used on a USB Flash Drive. http://www.lostwindowspassword.com/ or http://www.recoverlostpassword.com/products/windowspasswordrecoery.html