The best advice I can give is take the motherboard completely out of the PC and stick it on the plastic bag that it should have came in or on a piece of cardboard/wood (Anything with no metal in it) make sure the CPU and Heatsink are securely fashioned. Remove the ram from the board and hook the power switch cable and the speaker cable from the case up to the correct pins and plug the power supply in. Try to turn the computer on and if you still don’t have any power it’s the board or processor. If the system comes on with a long beep then it is because you have no ram in there and that is likely the cause of the system problems. If you still get nothing take the CPU out but leave the heatsink fan plugged into the correct power port and try and power it up. If you get no beeps this time your board is fried or it’s a bad power supply.