Solved: Log in screen doesn't come on

I want my computer to show the log in screen when I turn the computer on. There are 2 users (counting myself).

I log off at night -- it shows the log in screen, then I shutdown. When I turn on the computer in the morning, it goes right to my desktop. I do not want the other user to have access to my desktop. I have to click "Log Off" or "Switch User" for him to log in to get to his desktop.

I've researched and can't find a solution for this. Help!