thats crazy. i would only do that to a machine if i had the money to have another one, incase a freid it.
my friend has a 3.4ghz prescott and he tried to OC it, blew up his motherboard.
it happens from time to time. it depends in part on your motherboard and in part on how smart you are. if your setting out on record breaking attempts you need to heatsink all the voltage regulators
. even then it depends on your motherboards design. i know a guy who blew a voltage reg on phase change cooling with a high clock on an e6400. regulator just fried from the current pumped through it.