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[color:"orange"]That small fan atop the motherboard's onboard chip does not spin.[/color]

Do other lights and fans come on? A bad power supply can light LEDs and turn fans, but not allow the system to POST.

Did you try a different power connector for the fan? For that your motherboard would have to have another fan connector close enough, or you would need an adapter to plug it into a 4 pin connector from the power supply.


[color:"orange"]So now I need to practically rebuild my computer by removing and replacing the motherboard.[/color]

The recent symptoms are consistent with something overheating and possibly becoming permanently damaged (not sure if current chipsets get that hot). The occasional boot problems you had from the start could be due to a bad power supply (though I suppose a loose connection somewhere could behave that way, as well).

Before replacing the MB, try plugging in a different power supply, if possible. You would only need to connect the MB, main fans (if they don't connect through the MB) and the video card (if required) to check if it will POST, not hard drives, etc.
All the other lights and fans come on. The fan which does not spin is a fan which comes with the motherboard already attached. It sits atop a VIA chip I believe. I actually had trouble with it early on -- it made awful noises. After a time the noise stopped and I assumed that it was running ok, but it might have simply stopped functioning and caused some overheating damage. I should have another power supply I can scavenge from an old computer that I can try. I'll see what I can do. Thanks for the suggestions.

The question is not, Can they reason? nor, Can they talk? but, Can they suffer?
~Jeremy Bentham