Sorry about my absence from posting here, but my computer contracted a serious case of dust-itis (processor/ motherboard liable to overheating as a result so the machine didn't function!) and needed to be replaced. It stopped working on Monday 19 February so I took it in to our local Computer Shop and they investigated, arriving at the above prognosis. Well, the machine was 5 years old! So on 21 Feb I ordered a new PC to be built and have just taken delivery. Thank you, Computer Shop!
Back to normal, thank goodness.