I need help diagnosing a motherboard vs cpu issue.?

You found a voltage chart for a HP power supply? ok, well notwithstanding that this is just about impossible, if the computer is doing "nothing" as you say, regardless of your tests, the power supply is dead. Are the fans spinning? If not you can be sure it's dead, and if they are there still may not be enough power to run the computer. Is the CPU fan all clogged with dust? If it is, it may have overheated to failure, and this will cause a computer to do nothing at all. Although the fans should run.