I have an older Compaq computer (About 4 years old. It is running an AMD K7 700. It was working OK, but it is in a factory setting so cleaned it just using compressed air. Now it will not Post or show anything on Monitor. I took out all cards including Video, disconnected all cables and power connectors to drives. I replaced the PS, Memory and reseated the CPU. Nothing. The fans start, but it will not post. Any ideas?