Don't want Vista to shut down

Can someone tell me how to get my Vista Home Premium to act like XP when I leave my laptop at the end of the day.  What I want Vista to do is really nothing.  When I finish with my computer I want to walk away and have a screen saver come on and when I come back the next day, the next week or whenever, I want to touch the mouse and have the same screen appear as when I left the laptop. 

Vista now must log itself off as when I come back I see the icon on the screen and then I have to enter a password to sign on.  I don't want to see this.