|Why would you assume that your motherboard is bad?|
How did you test the power supply that you are sure that it is good?
Did you install the CPU heat sink with the proper amount of thermal compound? Look: http://www.arcticsilver.com/methods... Select your CPU and read the appropriate instructions.
Have you installed HWMonitor, SpeedFan, or other temperature monitoring program?
Have you recently added or changed any hardware or software?
Is your power supply powerful enough for your system and graphics?
Have you tested any other components?
Post your FULL system specs including make and models numbers (everything), any added or changed components, FULL ratings on your power supply (not just wattage) from the label, and much more details about the problem. Include whether the system ever ran correctly, when the problem started, any hardware or software changes since then, and all small details.
You have to be a little bit crazy to keep you from going insane.
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