You should be able to leave the laptop face up, as long as it's on a hard surface where heat is able to escape from the bottom.

There really is no need to turn it upside down to allow heat to escape better, if anything this will only make the LCD more apt to going bad or getting "key screen" meaning you'll be able to see outlines of where your keyboard is actually on the screen.

I would elevate the unit an inch or two, so that there's more airflow underneath the system.

Make sure you don't block any vents in the process, of course. If you visit fatwallet.com today (July 20, 06) and click on "Deals," there's an offer for an Antec notebook cooler for $10 at Staples. This might interest you.

it would be hard to read up side down.

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@alex_l wrote:
Is this a good idea?

I'm having my inspiron at 100 percent CPU performance since 8 days/nights (render job)
At night times when I'm not working, I'm turning it upside down, so the heat can go off better.

Is this a good idea?

I have heard if you use heatpipes upside down it would push the gas or fluid to the wrong side of the pipe causing overheating.

Is this the case with the inspiron 9300? Would you recommend turning it upside down.

Not having any problems so far... and it's "cold" in the morning, compared to the heat I can feel on the bottoms surface during daytime.

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You could try dipping it in a bucket of water - this way there won't be any need to turn it upside down!