We will monitor system and the home button is so close to the edge of the screen. I sometimes accidentally click on the right hand monitor and lose what I'm working on. How do I move the home button back on the left, were it belongs

I am using a dual Monitor display, and when I sometimes click on the home button my mouse moves over to the right-hand screen and changes what is on the right hand monitor. I would like to move the home button back to the left side of the screen where it was on Firefox 3. How do I do this