Presumably this is not very good for the CPU. But will it last >about a year under these conditions? What about other Intel CPU's? A >Celeron? A gigahertz processor? If I underclock these things as far as >they will go (on my mobo this means 66 MHz bus speed), will they run >reliably without active cooling? Do I need a special heatsink? Where >can I buy one? And so on. WHY? a cheap fan will cost you what $20?