David writes in with a troubleshooting question:
Question:The PC will not boot. The HD LED light flashes and the Power light Flashes. I thought that it was the power supply, because it was not making any noise and the fan was not moving fast. So I replaced it. Any ideas?
Answer: I'm assuming the power supply is working now but the computer still wont boot? If you see the hard drive light flashing and the power and reset buttons work then you know the motherboard is getting power. Even if the hard drive was bad you would still see something on the screen from the motherboard.
If the screen is blank then there are a few things it could be. It could be the video card, or if you have onboard video then it could be the video connection on the motherboard. Try taking the video card out and re-seating it or putting it in another slot if its a PCI card. If its an AGP card or onboard then you cant do this. It could also be bad RAM. You can try and take it out and re-seat it or try replacing it. It may also be a bad motherboard or processor. If any of these are bad you wont see video on the monitor. I suppose there is a slight chance that is the monitor but that's usually not the case.
Make sure your CPU fan is also working. Run the computer with the cover off and check it. If its not then you may have fried your processor.
Hopefully this will give you some ideas of where to look. Unfortunately there is no one answer to this type of problem.