Dear PP and Gerbil, Many thanks for all your help. I am sorry that I have replied only now. This is because I am also coping with the demolition last week of my conservatory and all the dining furniture in it by a stolen vehicle, i.e. getting quotes, seeing surveyors etc.
That has to be a real hassle!
No worries on our side - we forum veterans are used to sporadic replies and realize that "real life" always takes precedence...
The only time that they are problematic is when a poster is doing all sorts of "fixes" on their own in between those replies - that just serves to confuse us.
I followed your advice, Gerbil, and Backed up half, and then half again, re-booting each time. Actually as an Operations Research Scientist I ought to have remembered that this is one of the standard procedures in Search Theory. However, somehow or other the problem disappeared and did not re-appear even when I got down to the last '04' entry and so I cannot pinpoint what was causing 'Common' to show at start-up. I am grateful indeed to you both.
That is indeed odd, given that all we did was remove a bunch of registry keys and then put them back just as they were.... Oh, well - sometimes it is better not to question the how or why and just keep our fingers crossed that the change sticks ;)
However, another problem is current as well …