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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