If you don't know the password for any account in the Administrators group and are using a Windows XP based OS (XP or XP Professional) try this:
1. Put your Windows XP setup CD into your CD drive and start or restart the computer.
2. Either go into your system's boot options and set it to boot from CD, or you may be able to just press a (specified) key to boot from CD.
3. Windows Setup will perform some setup checks and load some files. You will see information about this. Be patient.
4. When prompted, press Enter to setup Windows, then press F8 when asked to accept the Licensing Agreement.
5. You will see choices listed, pick your install of Windows from the list, then there will be several options. One will be "Repair". Choose the Repair option. The Repair option will check the system and copy some files, then eventually reboot. Be watching for this.
6. When you see "Installing Devices" at the bottom of your screen, press Shift and F10 together. This will start the Windows command console.
7. At the prompt, type nusrmgr.cpl and press Enter. The User Accounts manager will start.
8. Find the account that you have lost the password for and click on it. Change the password as described above. Close the User Accounts manager and exit the command console.
9. Let the Repair process continue. You will be asked for the Windows Product ID Key, so be sure you have it.
9. When Windows starts after Repair is completed, you can log in to your account with the new password.