Went to turn use my HP Pavillion 400 Desktop this morning and it would not power up. The power button light was flashing but the computer had no response to the mouse or keyboard. I tried to give it the one finger reboot, that had no effect so I unplugged the computer from the powerstrip.
Once I tried to power back on not even the light on the power button worked. The green light near the power cord was on steady green.
Replace the side panel, plug in the power cord, and examine the light on the back of the power supply:
If the LED is on solid, the power supply is probably good and the problem is most likely caused by a defective component (processor, memory, PCI card) or a defective motherboard. Have the computer serviced, or remove the components and replace them, one at a time, to find and replace the defective component.
So the question is what to replace? I have taken out the, hard disk, the mother board, and the SDRAM is there any way to determine which needs to be replaced? Is there a more likely failure to start with? The diagnostic instructions above kind of rule out the power supply is that reasonable?