.. Go to the Start Menu and the Run box.
.. Type in the following:
control userpasswords2
.. now click OK
.. In the new Windows that appears select the account you wish to make the
primary logon.
.. Now uncheck the "Users must enter a username and password..." box.
.. Hit Apply and a dialog box will appear asking you to confirm the
selected users password.
Click OK.
The changes will work the next time you restart your computer.