|clarkent, please start your own thread.|
Hundreds of people have had the same situation you describe and troubleshooting it has been described in this forum as many times.
The fact that you see some motherboard LEDs means only that some power is getting through. It is no guarantee that your powersupply is fully functional.
It is highly doubtful there is anything wrong with your start switch.
To troubleshoot fully you need access to some spare parts that you can swap in/out beginning with a powersupply.
Disconnect from mains power. disconnect power & data cables to all optic & hard drives. Remove all but 1 stick of RAM. Remove any/all PCI cards.
Leave only motherboard with CPU & heatsink fan, Graphics, keyboard and 1 stick of RAM.
Now connect power and try to start up. Any beeps? Any fans running?
Goin' Fishin' (Some day)