Some piece of hardware is definately shorting out the system when you start it up. If you get power to the mobo (led on mobo is lit up) that means that power is being received at the mobo. When you turn on the pc and it starts up, then either something is shorting out or the Processor is overheating very fast. Although I thought that if the gell was bad or dried, the processor wouldn't even start. Just a thought.
As the sun sets, the earth shall prepare