This could be any number of things.
Try a different (but definitely make sure it's compatible) power cord.
Remove the battery and see if it boots without it (plugged into AC of course).
Does the laptop boot through BIOS and then stop? If it does then your Windows installation could be at fault and need to be repaired or reinstalled.
Are there any beeps? Beeps are the motherboard telling you what's failing depending on the beep sequence.
Could be bad RAM, try removing one module and trying to boot. Test them one by one, trying each module in each slot. Make sure there is no power to your laptop while you switch modules.
It could also simply be part failure. With the microscopic size of components on the motherboard it can be next to impossible to look at something and see that it has failed.
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