My PC does not ask password in Login even if I set it to ASK on login

When I first installed Ubuntu 11.04 I marked NOT to ask password in login. Then, ofcourse, it didn't ask me password on login. But now I want the OS to ask login password as I have many critical datas stored. I changed the settings to Password: Asked in Login but it doesn't work. My Ubuntu doesn't ask password in login. What should I do now?

I had same problem. Try running this command:

sudo gpasswd -d $USER nopasswdlogin 

this should work.

The thing is that my user was in the nopasswdlogin group. I had to install the gnome-system-tools which has the GUI to manage users and groups. Then I ran the users-groups manager and change my user to NOT be part of the nopasswdlogin group. Problem Solved.

Go to

System Setting -> System -> Login Screen -> Unlock

You will need to enter your password.

Then select the option that says "Show the screen for choosing who will log in"