1.Click Start, and then click Run.
2.In the “Open” box, type control userpasswords2, and then click OK.
3.Clear the check box for Users must enter a user name and password to use this computer, and then click Apply.
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4. An “Automatically Log On” window will appear. In the dialog box, type the password for Administrator in the Password box, and then retype the password in the Confirm Password box.
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Normally, the User Name field will auto fill with “Administrator”, the default super user account in Windows XP that does not come with any password (and normally use as a backdoor hack access to XP system). If you wish, you can change the user name to another user account.
5.Click OK to close the “Automatically Log On” window, and then click OK to close the “User Accounts” window.
bacteria comment: you can try this method on windows vista.