.It wasn’t .the motherboard or OS installation or the power supply per se.
At first build..
- Two SATA cables coming from the power supply, one to the two hard drives, the other to the SATA DVD drive.
- Two Molex power cables coming from the back of the power supply, one to two fans of the four fans and the power to the X-Port/USB circuit which also provides extra power to the front panel USB ports. The other was folded away..
I added a third hard drive, and used the SATA power cable from the DVD drive because I had considered maybe installing a fourth drive.
So, power for the DVD drive was supplied by a Molex to SATA cable adapter to the same Molex cable supplying the fans and X-Port. This is the point at which shutdowns started when a USB device was sometimes used from the front panel. At the time, I blamed the USB ports and had CoolerMaster send me a new front panel.
No joy yet.
The Great Driver Crash of a few days ago, and the actions I made while waiting for the hard drives to be checked by the other computers here, solved the problem without ne realising what I had done. Had I not brought the second Molex cable into use in a bid to tidy up the bottom of the case, it would probably still be shutting down.
But it isn’t, and it hasn’t cost me shipping of parts or buying new. The cash ‘saved’ can now go to something really useful.
Everything works, just like it did at first build.