If you wish to cool PS3 after overheating, switch off tumbler behind (near power cord). Now hold and do not release the standby button on panel , and then turn on tumbler. Cooling on full speed will start, PS3 will cool down, the red or green light will begin to blink (I do not remember).
After cooler stops.. Switch off the switch (near power cord) and then switch on again. Now you can play. If an overheat again. Do the same operation. (FOR PS3 40gb)
Well I have had mine since the first ones were shipped and mine still has not overheated, but I do have a couple of friends who have had their ps3 overheat, so its kinda weird but they make an intercooler that you can buy for just that reason!