Your problem is that your power supply hasn't got enough wattage. For the rig you described, having a 350-watt power supply is the bare minimum, and even that may not be enough juice depending on how many peripherals you have.
Check your power supply rating on that machine. If you've upgraded to a new board, video adapter, and processor using your existing ATX case and power supply, you probably have less than 300-watts, which is not enough to make the system boot.
Replace the existing power supply with a 431-watt Enermax.
The processor is the component least prone to failure in any PC-based system.
There is likely no damage done to your system by under-watting it.