Well, sometimes you just have to bite the bullet, grab the bull by the horns, etc. etc.
The repair install fixed it.
Had an error message at the end saying .NET framework 4.0 was missing essential files and it was being repaired.
I think that may have had something to do with my problem though how they went missing....... Just for point of interest. Update for Windows (KB971033)
was automatically installed during the repair install and yet it's not supposed to be compulsory, Along with Update for Windows (KB958488)
. Anyway. All's well that ends well.