Hi RadYew. Thanks for replying. I’ve actually already fully uninstalled Flight Sim and tried a reinstallation. What I meant in that line was that the flightsimulator.exe program won’t run at all, so although I can install that little file through Steam - about 1.5Gb - because it won’t run, the actual Flight Sim (~90Gb) never gets downloaded at all.
I think in the end, given I lack the technical skills to follow any but the most step-by-step instructions, which would just drive more skilful users here crazy, I’m just going to conclude that FS is incompatible with my PC, and go back to X-Plane. It’s just not as pretty.
But thank you all for your suggestions, I appreciate them very much. 