What can four years of not cleaning do to your CPU’s heat sink?
The CPU was reaching temperatures of more than 100 degree Celsius at which time it would reboot.
Upon opening the heat sink was found to be clogged with dust. Cleaning it resulted in collection of this much dust:
1) Clean your heat sink regularly
2) If your PC abruptly reboots, it maybe time to clean the heat sink
My PC has been running smoothly since with max temperatures going only upto 60 degrees C.
Also posted at http://deepra.com/tips/