The current crop of P4 CPUs (except the "M" class) use over 100 watts of power. In fact, they generate more heat than a kitchen hot plate.
Intel specifies that the internal temps of the case should remain near 40 Centigrade.
Typical cooling mechanism is to force hot air out of the case with a fan, allowing cooler air to enter.
Modern cases include multiple openings for air flow.
Fans alone aren't enough, so modern PCs have heat sinks that "absorb and dissipate heat produced by electrical components."
Cooling Fins that transfer heat away from CPU. Rely on convection (warm air rising away)
Heat Pipes - small tubes filled with fluid that expand and rise to a different area for cooling. (No pump needed).
Water pumps - typically just for gaming PCs.
Peltier coolers - different mechanism than convective coolers (which won't work when the outside air is warmer that the air inside the case).
