Take out the ram, rub the contacts with an eraser,
put it back, shake it abit.
(if you have 2 rams, take out 1 and try, maybe one of them have
spoilt)
If you are using a graphics card, take it out and try with
onboard graphics
If still cannot, unplug the powercord, press the power button a few
times to discharge the system. Then clear the cmos using the jumper
and try
If you know how, unplug everything inside and test ur mainboard
with another powersupply.
I only can pass till step 2 if it was me