Thank you all again for taking the time to look at this problem.
In particular, thank you to Orbital Shark, because after changing that setting I can now see the folders on the D drive and I seem to be able to drill right in as far as the user files, which seem to be there unharmed.
Two questions arise.
First, how did the hidden attribute get on to every file? I am following Golden's recommendation and running the eset online scan, but it will take a couple of hours to complete.
Second, how do I get it off most files while leaving it on important system files. I was tempted to take it off everything, but it won't let me (see below).
But if I navigate to a documents folder, I can take it off everything there (see below). But it will take a while fixing all the folders that need fixing (desktop, favourites) individually.
Does anyone know of any shortcuts?