Can we turn off screen on XPS 1640 when using external monitor ?

I know i've seen a post about this somewhere, i just can't find it anymore.
I am trying to turn off my XPS 1640 screen when playing on an external monitor. I tried "nircmd" but it turn off both internal and external monitor so it's useless. Will the laptop overheat if i configured it to do nothing when i close the lid ? Any other way to turn it off with the screen up ?

Thx

 

When I connected a TV to mine I pressed that monitor key on the keyboard and it works, even if I leave my laptop open. Probably not a good idea to keep a laptop running when the lid is closed since some heat does dissipate from the keyboard.

 

Wouldn't the vents be more open though?

 

yes you can turn off the monitor and use the external one but i would recommend you not to close the lid, right click on your desktop click personalization(properties if you are on windows xp) when the new windows comes up select display settings(only on vista) once the display properties window opens click on the settings tab and make the external monitor(generic pnp monitor) the main monitor by check marking one of the option and for the dell monitor(graphic card name) uncheck mark both of the options, wish i could show you pictures or give you more detailed instructions but my laptop is not working

no you would end up making more work for the vent fans and would probley cause your system to overheat if it was on for a long period of time, the keyboard and screen would become extremely hot if you left the laptop running and closed the lid

 

What key are you talking about ? Is it the one next to the F12 key ?
If that's the one, nothing happens when i press mine. Do you have to press it in combination with another key ?

 

It doesn't let me put the checkmark to set the external monitor as the main monitor, and it doesn't let me unchek the 2 checkbox for the Dell monitor