A friend's PC has problems booting and has been steadily getting worse according to him. When I started it today, it took about 5 minutes before it shut itself down completely (power off, no LEDs on the front, no fan noise, as if someone had held down the power button for more than 5 seconds). When switched back on, the BIOS reckoned that the processor had overheated. The HSF is clean (ie. no dust) and the fan is able (and is) spinning, no dodgy fan noises either. I took the HSF off, cleaned off the old paste and re-applied it. The system still had problems starting, again citing the CPU overheating. It wouldn't let me into the BIOS setup at all (I wanted to check the sensor readings myself). It would then auto power off. Considering that I removed the HSF soon after I last started it to clean up the paste situation (both HSF and CPU), I didn't feel much warmth from either surface then either. The HSF feels secure before removal and reconnection. I did a BIOS reset (CMOS jumper), which allowed me to get into the BIOS setup. Sure enough, the processor temp says 76 - 80C depending on how long I've risked leaving it on for. However, the HSF is completely cool, as if the system has been off for hours. There isn't much heat radiating in that general area either (a bit around the capacitors between the CPU and rear I/O panel, but not loads). I am wondering what to do. Could a sensor have malfunctioned and that's it? Unfortunately I haven't seen an option in the BIOS yet to disable auto shut down to test that theory but it seems like a risky theory to test. Ideas? What's the expected operating temperature of this CPU? I'm thinking that the overheating message is bogus and the BIOS was just having a fit and needed resetting. The processor temperature is getting higher than even expected for this CPU because I'm in the BIOS and the processor tends to run full whack when in the BIOS.