Battery Questions

[gopher2011]

So i think the battery on my 6700 is a dud or something. I charged it up until the green light goes on and all night for that matter, then i woke up went to my first class and then in my second class at like 11:30 it said battery is very low.
So my ? is, is there some sort of setting that i am missing here that can save me battery life. I know that you press the power button for the screen to go off, but otherwise is there a place where i could get a good new battery?