The PC is working again! My friend, Mark (who knows a thing or two about computers) suspected a faulty lead inside the machine. We got it going last night, but it relapsed overnight and further investigation was required today. Finally, I tracked it down to one of the fans and disconnected it. Problem solved. It is working reliably again. No need to worry about cooling. The machine was designed for gaming, so it is chock full of fans. The most graphically demanding use I ever put it to is watching YouTube videos, so it is more than sufficiently equipped to do that.
Now I can get back on with editing. Hopefully, I will be contacting Cuzzie for a proofread within a few days.
Writer of Fantasy, thrillers, comedy - and anything else that takes my fancy.