|Thank you for your quick and excellent responses. I will try to answer all your questions and to provide maximum detail.|
This very basic system is less than 3 years old; it was custom built with the following components:
Gigabyte GA-G41MT-S2P Mobo.
Intel Pentium Dual Core E5800,
4GB DDR3 RAM;
Seagate ST35004 500GB HDD;
Lite-on DVD Dual layer DVD;
no external GPU.
Last month it was upgraded to Windows 10 Pro with no problems. The case has never been opened until this problem. Computer has worked flawlessly until it would not boot.
I have tried various things: disconnected HDD, DVR, monitor, keyboard, mouse, removed RAM, removed CMOS battery and had only AC power connected.
The computer appears to start (blue led on switch turn on, fans run, led on DVR flashes) but then within 2 seconds, the blue led goes out, fans lose power for about a second or less then they all start up again to fade out as before. This goes on until I hold the power button in to shut down the computer. There are no beeps, the monitor registers No Signal. “Paper clip” test works.
Hope this info helps lead to a solution.