I've got two laptop computers with dual monitor's set up, but disabled. One has a cable to my TV, if I ever entertain or something. I used to use it a lot more when the TV was my only monitor.
The other set up is for catching media player TV all day long, by which I study Hebrew. I also disabled the dual monitor properties, so both screens show the one desktop area. My puny computers can't handle my daily work and Media Player at the same time. Ok...here's a biggie, I found a Sony 18" flat screen marked 'Broken' on the side of the road one day. The only problem was a very slight buzz, that was inaudible from a few feet away. So the poor boy has a mounted LCD on his wall!
Sorry I'm talking in circles. The point is I used them for awhile, and the one tool I found indispensible was Skrommel's <a href="http://www.donationc...ouse>ConfineMouse
It's the toaster to bread. If you just really use one of your monitors to display, make sure you have that program.
At one point when I had the used the first set-up, I had a sliding Rainlender ToDo list on the right side of my primary. Without ConfineMouse, I couldn't have scrolled down my list. Every time you go to close a window, the mouse gets lost on the second monitor, which is a big pain if they're not side-by-side. I would have had to ditch my beloved desktop setup, of Rainlender there. I can't heap enough praises.