power supply or mobo hardware problem... not sure

my PC turns on(fans go, hard drives spin) immediately when i flip the power supply switch on the back of the power supply. usually i flip it which makes the mobo LEDs turn on, then press the button on the front of the case to actually turn the computer on. i dont know what would cause this to be.

once i flip that switch and it turns on, nothing comes on the screen and the computer doesnt post. im thinking its some kind of bad power supply, or some sort of mobo problem controlling the power on and off or something.

any suggestions?

 

The motherbaord will light up when the power switch on the back is on. This is for wake on lan.
Boot with a known working stick of ram and graphics card.
Troubleshooting hardware problems is fairly easy. Take all addons out except for what I said above. If it gets to the bios put in another component and try again.
I doubt you have a ps problem. More than likely it's a bad stick of ram or video card problems.
Do you get any error beeps?