I had an Athlon board that one of the little plastic tabs that the fan/heatsink clips to snapped off. The motherboard had an automatic shutoff feature that would shut it down if the CPU fan dropped below a certain RPM. But since the fan kept spinning at full speed, but was just dangling inside the computer, not attached to the CPU, it melted the core. If anyone wonders what that actually looks like I think I've still got the processor at work.