2010 iMac won't go to sleep

2010 iMac and I cannot make the computer go to sleep. Instead, I have to shut it down and power it up when I want to use it otherwise it will run non stop in the background with the display turned off.

I'm in utter disgust in the fact I have to pay to keep the thing running or turn it off to save electricity. My house doesn't send a lot of air to that room and the heat in conjunction with it never shutting down makes the room too hot.

FIX THIS APPLE! Really want to upgrade to Lion and uninstall this $20 piece of garbage. But that would be a load of even more work. How come they think we are beta testers?