OK - I can see that all the folders immediately under my user name Neil on the desktop have been emptied - but the contents are still present under c:\users\neil.

I thought that previously, one was a shortcut or alias to the other, because they all held the same stuff.

Since the user folder structure was empty, I suppose Windows reverted to some defaults. Does this imply that some link between the folders and aliases got broken during the update? It would certainly account for the problems.

Also, there were previously some folders to which I got "Access denied" but that has cleared. It still all looks like a Windows job rather a than malicious attack. (I do have Norton running)