Tom's Hardware did a special on what happens if you remove the heatsink from an active loaded processor... check it out here
http://www4.tomshardware.com/cpu/01q3/010917/index.html
They have a neat video of what happens...
http://www4.tomshardware.com/cpu/01q...tvideo-05.html (you'll need DivX, theres a link to grab it)
For those too lazy to click, heres what happened.
P3- proc shuts down and system locks up, needs reboot. Nothing burnt.
P4- proc throttles back as evidenced in Q3 slowdown, system keeps going, nothing burnt.
AMD Athlon T-Bird and AthlonMP: Core meltdown almost immediately (within 1sec of pulling the heatsink). Tbird measured at 350°. You should note that the light-colored stuff you see around the CPU core on the AMDs is not a melted core, but burnt thermal goo.