It seems that the VRAM on the EVGA GTX 1060 has failed so this possibly the reason for the crashing.
After removing the card and installing a spare GT 630 in the machine the HDMI can only achieve 1920×1080 and not many games will play on the old Fermi architecture.
The GTX 750 is in storage so it will be installed once it the box it is in is discovered.
The machine is now on the desk on its side pending video card servicing.
Checked and fixed a windows error. I also reinstall windows recently to fix other problems. This problem suggest graphics issues are plentiful.
NOT THE GTX 1060
With the machine using the GT 630, the same artifact is present. This suggests something other than the video card is causing the white dot on the top left are of the screen.
Testing the RAM showed no fault and a clean install of Windows did not help.
The dot is peculiar as it is present at boot before moving off the screen are to the top left corner but once Windows is at the main desktop it appears.