This sounds like a motherboard failure. Now it could be a jumper in the wrong place or even malware but details are slim so the most likely is an old motherboard that has failed in some way.
Bob
When i try to boot my computer, nothing at all happens. hard drives do turn on, fans don't spin, nothing. but, if i remove the cmos battery for 10 seconds and put it back in, the computer will boot no problem... i've replaced the battery and the same thing still happens. could it be psu related?

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