"As of 2015, FS2004 is probably still the most popular of Microsoft's simulators." (https://en.wikipedia.org/wiki/History_of_Microsoft_Flight_Simulator#Flight_Simulator_2004:_A_Century_of_Flight).
"Because FS2004 is probably
the most popular flight simulation package ever released, freeware
developers have released thousands of files that can be installed into
it. Many users prefer FS2004 to later releases of Microsoft Flight Simulator..." (https://flyawaysimulation.com/downloads/fs2004/).
CD case still wrapped in cellophane. Check OS & hardware requirements and compatibility before purchasing. Delivery is via post office registered mail.