Holding down Shift>Crtl>Alt and hitting the F6 key does exactly the same thing as Holding down the shift key and double clicking on the Deepfreeze icon in the Notification area. Two different ways to come to the same screen. Both will give you the password screen and if the password is set and not known you go no further. If this is his home computer and has set up a password and cant remember it then he is in a position where he has to format the drive and reload the system. Posts like the one above possibly has reference to someone wanting to unthaw deepfreeze for various reasons. School computers come to mind.
If a person installed this program on their home computer then it is unlikely that they would have forgotten the password.