Update on my computer. The hard drive has indeed failed. So ... a new drive (SSD 2TB) is on order from Amazon, and is supposed to arrive tomorrow. Then it can be installed in my computer.
While I could reinstall my runtimes, I'm hoping he can recover them so I don't have to reinstall. Of course, I can't remember where exactly they are ... other than in My Documents. But I can't remember if they are inside the Design 3D folder and whether there is another folder inside that one. Of course, I can't just open Explorer and look, because ... 1. The computer is in the shop. and 2. The Hard Drive failed!
I need to take screenshots and store them in Google!
Since I had to have my hard drive rebuilt some months (or has it been a year now?) ago, I have all my documents, whether text, Poser, Photoshop, Silo, etc., backed up with Google Backup & Sync. So, I've not lost any development work (or that runtime). I also now backup the AppData / Roaming folders, so I will also be able to restore the Photoshop and Filter Forge presets and filters.