re: heat dissipation

[Frank Sheeran <Frank.Sheeran@ska.com>]

Think of your computer as a fancy heater.  Basically, all the power 
consumed by your computer (say, from battery) is converted sooner or
later into 100% heat, light, and other electromagnetic radiation.
I'd guess the majority goes to heat.
 
That heat can either stay in the box and raise the temperature alot,
or the heat can come out of the box.
 
Given two comperable laptops (both with laptop-engineered Pentiums,
equivalent memory, etc.) you'll get more or less the same power
draw.  One that has the equivalent of sleeping bag insulation built
into the case will feel nice and cool on the outside and be hot 
inside.  One that was designed to push this heat out will therefore
be cooler inside.
 
In other words, the hotter the case, the cooler the internals.
 
Air is an excellent insulator.  Most sleeping bags, in fact, just
use various materials to halt convection, keeping the air in place
to increase efficiency.  Any solid I can think of would probably
be better.  If your lap is getting hot, that is a sure sign that
you are sucking heat out of the computer, through the clothes or
blankets.  Uncomfortable, yes, but probably indicates your computer
is cooling properly...

Frank