Laptop won't sleep when lid is closed?

I have a Lenovo P400 with Windows 8 and just today, I experienced the laptop not going to sleep when the lid is closed while plugged in. If it is running off of the batter, it sleeps, but not when I have it plugged in. I don't remember changing any settings, and I just started experiencing this. Nothing is blocking the lid by the way

Added (1). After I posted this question, I looked more into it and did that, my computer is already on that setting. It says sleep when lid is closed (plugged in). I'm not entirely sure why it stays on when I shut it, do I have to reset the computer or something?

Guest

My computer now does not hve the option of choosing 'sleep'or 'hibernate' - just 'shut down' or 'do nothing'. Thoughts?

Bruce

Go into Control Panel --> Power Options. On the left, click on "Choose what closing the lid does". Click on the drop down menu for "When I close the lid" and choose "Sleep" or "Hibernate".

rahul