Buy "Microsoft Flight Simulator 2002" from Amazon,
MS FS2004 will perform a lot better than FS2002, and there are folks running it on Win 10, as well as Win7. Also there are probably as many or more free downloads of aircraft and scenery for it than most of the others. In fact there are a lot of folks still helping support it on flightsim.com, probably other sites, too, and with decent mesh scenery it'll look somewhat better too. And I don't think purchase cost would be much more- in fact Amazon has it new for $69.88, might be on eBay for less.