Has been trouble free for many years until today when it wouldn't power up this morning.  Quick troubleshooting and the power supply was good.  It finally started after I cut the power supply green wire going to the motherboard, grounded the green wire side leading to the power supply, and then depressed the power button at the front of the desktop.  Only this way is it starting, just pressing the front power button has no effect.  Turning off, I depress the power button on the desktop.  Then, when the motherboard seems to be disabled (and the power supply fan speed greatly increases), I then unground the green wire going to the power supply.   What is the problem, is the main power switch partially faulty somehow?  Seems like its activating the PC, but only after I have grounded the green wire manually.  Thank you in advance for any help and solutions.