MacBook – How to disable the Macbook internal display and only use the external display on Snow Leopard

I've taken up olivier's suggestion to arrange my monitors to eliminate a common border:

I chose the bottom right because I keep my dock on the left hand side of my screen, and I use my upper right as a hot corner to sleep the display. I also moved the menu bar to my desktop monitor and the MacBook screen is completely dimmed.

There was another option I heard about: using a magnet to make your MacBook think that the lid was closed. This does work - I placed a snippet of a refrigerator magnet near the bottom left side of my keyboard and sure enough my MacBook thought I had closed the display. Unfortunately, Mac OS X also disables keyboard and trackpad input when it thinks the display is closed, so this option didn't work for me.

I would pay attention to two factors:

1) Do you have an external keyboard attached?

2) The power situation - how/when sleep happens is affected by this

3) If the lid is closed at the time you move the mac.

A couple of examples will help illustrate this:

Recently I found that my external keyboard was not waking up the closed lid mac as I thought it should. I found that this was because the power was unplugged and the 'lid closed' operation only worked with the power actually plugged in.

As another example I found that when my computer was asleep, in order to wake it up - without opening the lid! - the trick was to plug an external keyboard/mouse in and hit a key / move the mouse. This then took the mac out of sleep (though again that may depend on whether you have power plugged in or not).