@JCBeastie heat pipes have operational temperature limits, too hot or too cold and they wont work (although for a laptop too hot or too cold might not be a problem, depending on how well the heat pipe was designed). These limits are usually within 20degC for laptops and the like. heat pipes which are too long can be limited by their wick's ability to transport water. a heat pipe assembly as long as the water cooling loop pictured above would need a fairly advanced (i.e. expensive) wick (I'm not saying it would be more expensive than water cooling). assuming the cooling system is overloaded heat pipes fail much more dramatically than water loops. when a heat pipe's heat carrying material cannot find a place cool enough to condense your basically cooling with straight copper or whatever the pipe is made of (that's usually very bad). When a water cooling loop is overloaded the water is able to absorb an impressive amount of heat (depending on how much water is in the loop) before it boils or causes the PC to shut off. So while heat pipes win in terms of maintenance, general cost, whatever.. water wins in terms of temperature range and loop length (also longer loops enable better radiator positioning, and with better positioning comes potential for bigger radiators). oh and also with water loops you don't have to be as careful about where your radiators are relative to multiple components. also a major advantage to water cooling a laptop is that it is just plain cool.