OK, so I uninstalled Obsidian, after copying and saving the Obsidian User folder elsewhere. I then reinstalled and selected the option to go to the Demo/help vault rather than creating a new one. I then had Help of course
I then created a new vault and moved my old data files into that. So I am good now
How my data files ended up in the Help folder originally is a mystery. I do know that on the original install, I selected the Create Vault option and that did create my nominated ‘Obsidian Data’ folder on my D: drive. It was still there after I uninstalled Obsidian, but with no data in it of course. Frankly, I had forgotten I had created that until I went to create the vault following the reinstall, only to discover the one I originally created
One for the X files seems like
Thanks again for your help @sam.baron