Docked To The Wrong Place?
Some users have reported that Microsoft OneNote 2010 is docked to the wrong part of the screen - usually the top - and they can't see how that happened or how to put it back.
How it Happened
It most likely happened because you, probably inadvertently, dragged the title bar of the docked window to the top of the screen and dropped it there. OneNote will re-dock itself to the nearest edge (yes, even the bottom) when you do that.
Rather helpfully it remembers where it was so if you un-dock OneNote and then later re-dock OneNote it will go right back to where it last was. In this case back to where you didn't want it.
How to Fix It?
You actually fix it the same way you did it to begin with. Grab the title bar of the docked OneNote window (The title bar is across the top) and drag/drop it back to the edge where you want OneNote to dock.
Simple as that!