Update:
I replaced the cable to the front panel and pushed the power button and it came on and booted to the windows log on screen. However the USB key board is not operating, nor is the Bluetooth mouse as it connects through a USB powered transmitter.
I pushed the power button and the unit shut down. I waited a few minutes and pushed it again and nothing. I had to use the button in the rear of the machine to restart it. This time instead of a black screen it was totally red, but it booted to windows but the graphics were terrible. I had to unplug the power supply to shut it down. I reseated the graphics card and the connector to the monitor and tried to start it from the power button, but no. I had to use the reset button on the back.
It started and again booted to the windows logo on screen but the USB keyboard and the mouse would not work.
Unplugged it and tried the front button again and it started. Same thing. No keyboard or mouse.
Turned it off and tried to start it from the front power button, but no. Had to use the button in the back.
It seems all the USB ports are dead.
Anybody have a guess?