type in: control userpasswords2
up pops a handy little window
select the user you automatically want to log in as
uncheck 'users must enter a use name and password to use this computer'
it'll ask you for the password that it should log in with, and to confirm it.
This is for all of them. XP, Vista and 7.
Voila! No more log in.
Make sure you un-check 'prompt for password' in the screen saver settings as well, lest you be required to log in after your screen saver comes on.