[Tightscot]

Try this;

Click Start, Run and type CONTROL USERPASSWORDS2, and click Ok. Select the user account from the list (to which account you want to automatically logon). Uncheck Users must enter a user name and password to use this computer option, and click Ok. Type the user account password and complete the process.

For Windows XP Home, don't try to auto-login as the built-in Administrator, as you'll receive a restrictions error.