1) Go to the Start Menu and the Run box.
2) Type in the following:
control userpasswords2
now click OK
3) 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.
4) Hit Apply and a dialog box will appear asking you to confirm the selected users password.
Click OK when you are done!
That's it! You are now finished.....