close macbook when connected to monitor?

I've read that you can close a macbook when it's connected to an external monitor- and that all you must do to keep it from going to sleep is to hit a few keys on your keyboard.

This method is not working for me.
When I shut the lid of my Macbook 2.2ghz running OSX 10.5.5, it goes into sleep mode even when I press buttons on my USB keyboard.

Perhaps it's because I'm using such an old keyboard- the one that came with my old g3 iMac? Can anyone suggest a work-around?

You need to close the screen, let the computer go to sleep, then hit a key or a mouse button and it will wake back up. Be sure your monitor is connected.

yep, tried all that - still not working.

Are you on AC power? Clamshell mode will not work when the machine is on battery.

Make sure the external monitor is on and attached to your MacBook. Close the lid on the MacBook to put it to sleep. Leaving the lid closed, tap any key on your external USB keyboard to wake the machine. The external monitor should come on.

Also, you need to setup the external monitor to "mirror" mode.

Regards.

thanks- it's finally working!
I had to unplug the keyboard & plug it back in, then hit some keys.

Also if you just want to keep your Mac on when you close it check out a program called InsomniaX I use it and love it