OK, then do the following;
1 System OFF and pw cord removed from the rear of the pw supply. Press the ON button 2~3 times. This will remove any residual charge from the pw supply
2 Open the case and pull the pw connectors from ALL drives; both hd and optical
3 Remove any add-in cards. If your system has onboard or onchip video [unknown since you have not posted specs] Pull your video card out and connect it to the onboard port on the motherboard. Note there is a latch that must be depressed to remove the video card. Do not just yank it out; you will break something
4 Reseat ie remove and replace both atx and aux/cpu pw connectors on the motherboard. Be sure they are fully seated
5 Pull out all ram and blow the slot or slots out with a can of air. Reinstall ram and again be sure it is fully seated
6 Disconnect any usb device ie printer, hub, whatever. Leave the keyboard connected
7 Clear cmos with the clear jumper. Read your motherboard manual for detailed instructions
8 Replace the pw cord and pw ON. See if you get display. If you do, then shutdown and start connecting devices one at a time until you find the failed part. If the motherboard will not complete POST ie you get a display, then you will need to swap parts with known good units ie pw supply, ram, motherboard etc until you find the failed part.
