System turns on however hard

Turn power off and unplug power from computer.
Unplug printers,backup drives and speakers.
Open case and unplug power supply from the board.
plug power cord back in press the power button.
Of course nothing will happen.
unplug power cord again.
plug power supply back into the board.
plug power cord backup and press power switch.
If nothing happens unplug power cord again.
pull out your memory sticks and plug cord back in and press power button.
Of course not much will happen.
But really something is happening to your computer so continue.
Pull power cord and replace memory sticks.
replace power cord and press power switch.
Continue this pulling out pci cards one at a time until you find out what the problem might be.
Try different keyboards and mice too.
Good Luck