Windows 10 (Screw)update!
Well now, about two days ago there came a further Windows update(s), which perhaps not surprisingly stuffed the computer once again. At start up (after the update) the computer took over half-an-hour before it was usable, but did eventually settle down to a reasonable level of functionality. At the subsequent start up, the boot sequence took just over eight minutes to reach a usable state. Today, it took a mere three-and-a-half minutes - Not as good as it should be, but liveable.
The sound issue; Not as bad as it was! Off site audio appears to be normal once more, clean, clear and bassy again, without being OTT. Onboard, synthesised sound is dreadful, sounding like a cheap tinny radio halfway along a ten foot drainpipe! - I guess I don't need the games anyway! And, speaking of which, at the first game start after the second update, the games failed to start up completely and needed to be stopped and started up again. At this point all seemed normal, until the games' sound effects come into play, and that's where it comes to grief.
So it looks like a patch may have been applied - maybe? To fix the worst issues.