Whenever u install XP, it automatically creates a built in account called "Administrator". It has administrative priviliges. Most Windows users don't use this account since its not displayed on the welcome screen. One more thing bout dis account is that it is not password protected (until n unless u have changed the password).
To access this account you have 2 start XP in Safe mode.

To start XP in Safe mode:

1. Restart XP.
2. Before it starts to load, press F8 key continously.
3. A menu will appear. In that select 1st option ie. Safe Mode and press enter.
4. Next it shows all the Windows OS installed on your hard drive. Select the one of which you have forgotten the password and press enter.
5. Wait for OS to load...
6. On the welcome screen you can now see the built in Administrator account. Just log in...:)
7. If you have a classic logon then in User name field type "Administrator" and press enter...
8. Enjoy...:)