Gerry,
Thanks for your reply. Before I go into something new I found, please let me ask a couple of questions:
- What indicates a file corruption on C: drive going beyond Windows Update? I am asking this because, the system otherwise runs well, all application are working normally.
- Why not installing those 4 programs? Is there a issue with each one of them? I have them on a another PC, and there is no issue, though I have to say that I reinstalled W 8 and then W 8.1 some weeks ago.
I now have found a site that offers a W 8.1 Pro ISO file for free and it appears to be genuine, about just 4 GB. They also offered a link to the MS Store where a tool can be downloaded to make a USB stick bootable and copying the ISO file on the stick. The question is not yet clear what License I can enter. The one from the W 8 Pro DVD. Will see what happens. I restarted the PC with the USB stick plugged in and it came right away to start screen of the W 8.1. Pro installation. I stopped that, of course, because I have to make other preparations yet.
I'll come back to tell what happened.