I removed the battery, plugged in a new AC adapter (light glows solid around DC jack). When I press the power button it powers on, the fan spins up, then there is a quiet click sound from inside (near the DC jack area) and it immediately shuts down. I have removed the HDD, CD-ROM, and tried each memory chip by itself. So, I would think it is a problem with the DC jack, fan, motherboard, CPU, or video. Any ideas?