The guide at seekermeister's link worked, but when it asked for a password for the account I had to leave it blank since... well, there is no password on mt account right now.
Even your link says "If you only have one user account that is not password protected on the computer, then Windows 7 will automatically log on to that account at startup." Which is my situation exactly, but Windows 7 did not log me automatically, even though my admin account is the only account (guest is off and no others exist) and it has no password set. I even tried setting a password, restarting, removing the password, then restarting again, but it wanted me to log in still by just clicking on my account icon. It just bothers me, but at least I can manually set it to log me in automatically as if I did still have a password set.