Reset procedure: unplug, remove or disconnect battery. Hold the power button for 30 sec. Remove and reinstall memory modules and hard drive. Power on AC only - if it will, but won't with the battery, the battery is bad.
If it still won't get past POST, unplug everything USB and try again.
If you then still get nothing, it's likely a bad mainboard.
Yup....bad battery. When I removed the battery, I can boot. Even with AC power, the battery is interfering with the boot process. I don't understand it, but at least I can work. :-)