Disable auto login at booting ubuntu

I always fall in some peculiar problem. Last post I don't want to enter password everytime. But now I want to enable password based security. I am using Ubuntu 10.04 and thought my problems might occurred and solution will work for you too.

When I install Ubuntu I tick mark 'auto-login'. So I did not need to enter password everytime when machine start. Now I have an another user in my machine. She take sit infront of my computer everyday for 1-2 hours. So I create a new account for her. In this moment I need to disable 'auto-login' at startup.

When account was created then their is an option which need to mark as passwordbased login or passwordless login. My first account password requirement is disabled. Now do the step by step doings below.

Go directly to System > Administration > Login Screen

Login Screen Menu Item

You must enter password to unlock it before everything. Now check carefully whether anyone have permission to 'Auto login'. It might wrote as

Log in as (User name) automatically

Clear tickmark from it. Click to tick on the second option. Which is said:

Show the screen for choosing who will log in

Login Screen Settings

Now close this 'Login Screen' Settings and restart your computer. You will meet a 'Login Screen' to select yourselft from various user and enter password.