Try this trick and see if it works. log into any account that you have access to. Press Start -> Accessories -> Command Prompt. Now type "control userpasswords2" without the quotes. A dialog box will appear. Remove the check beside "Users must enter a password to use this computer". If for some reason it does not work this way then boot the machine to the command prompt and try the same thing again. It should allow every user to enter the machine without a password.
