a) click Start and type ‘netplwiz’ or click that name on the Start menu
b) in the GUI window that comes up, uncheck the “Users must enter a username and password to use this computer” box
c) click ‘Apply’
d) in the new dialog box that opens type the name of the account you want to auto-logon by default (if the account is not normally passworded then it blank)
e) click OK and exit