It has been more than a year since my last post and that computer has been retired. However, I still find it useful to run my new MacBook Air attached to an external monitor and with its internal display disabled. A few days ago, I found a better and more permanent solution than a flimsy magnet:
That's it. No magnets required.
It takes a little bit more for this to work under OS X 10.7 Lion, though. Entering the following command in terminal seems to do the trick:
sudo nvram boot-args="iog=0x0"
Undoing this is as simple as typing the following, also in terminal:
sudo nvram -d boot-args
You can also zap the PRAM (press Cmd+Opt+p+r at power up) to restore it to the new Lion behaviour.
This works great and I've been using it to improve my laptop's ventilation and wireless reception.
I first saw this documented here: Mac OS X Hints - 10.7: Disable internal laptop display when external display is attached
