Install FSX and FS2004 on the same PC safely using separate folders, correct patches and add-on paths, with fixes for common Windows conflicts.
Yes. FSX and FS2004 (FS9) can be installed on the same Windows PC because they use separate program folders, executables, configuration files and scenery libraries. Install each simulator into its own writable folder, patch each edition correctly, and keep add-ons pointed at the simulator they were designed for.
How should I install FSX and FS2004 together?
The safest method is to complete, update and test one simulator before installing the other. The installation order does not matter technically, but this approach makes any Windows or disc-related problem easier to isolate.
- Choose separate folders. For boxed copies, locations such as
C:\FlightSims\FS2004andC:\FlightSims\FSXavoid many permission problems caused byProgram Files. For FSX: Steam Edition, let Steam manage FSX inside its own library rather than moving the folder manually. - Install and launch FS2004. Run it once before adding aircraft or scenery so that Windows creates its user configuration. On a modern operating system, follow our FS2004 installation guidance for Windows 11, including the advice for legacy disc and permission problems.
- Apply the appropriate FS2004 update. Test a default flight afterwards. Do not start installing add-ons until the unmodified simulator opens and closes normally.
- Install and update FSX. Boxed FSX Standard or Deluxe normally follows the SP1 and SP2 update path, while Acceleration has its own sequence. FSX: Steam Edition already incorporates the relevant service-pack improvements, so do not apply boxed FSX patches to it. Our boxed FSX service-pack instructions explain the edition differences.
- Test both desktop shortcuts. Rename them clearly as FS2004 and FSX if necessary, then install add-ons into one simulator at a time.
Will FSX and FS2004 settings conflict?
No, FSX and FS2004 maintain separate executables, configuration data and scenery databases. Changing controls, graphics settings or scenery priority in one does not alter the other.
| Component | FS2004 | FSX |
|---|---|---|
| Main executable | fs9.exe | fsx.exe |
| Aircraft location | Aircraft | SimObjects\Airplanes |
| Main configuration | fs9.cfg in per-user application data | fsx.cfg, or a Steam-specific variant in some installations |
| Scenery | Its own scenery library and configuration | Its own scenery library and configuration |
A legacy add-on installer may still select the wrong simulator by reading an old registry entry. Always inspect its destination path: selecting C:\FlightSims is not enough when both simulator folders sit beneath it.
Common side-by-side installation problems
Most side-by-side problems come from an incorrect path, an outdated disc check or a legacy add-on trying to write inside Program Files.
- FS2004 will not start: some original discs use copy-protection components that modern Windows does not load. This is an FS2004 compatibility problem, not a conflict caused by FSX.
- An aircraft does not appear: check that it was not installed into the other simulator or placed one folder level too deep.
- An add-on reports Access denied: reinstall it to the correct writable simulator folder rather than weakening Windows security for the whole PC.
- The wrong simulator opens: recreate the shortcut directly from
fs9.exeorfsx.exeand label it clearly.
Can I use the same add-ons in both simulators?
Usually not without checking compatibility first. FS2004 and FSX use different aircraft structures, model features, gauges and scenery capabilities, even when an older add-on appears to load in both.
Keep separate copies of aircraft, scenery, gauges, modules and AI traffic. In particular, an FS2004-format AI traffic file placed in FSX can stop FSX-format traffic from appearing. For aircraft that claim cross-version support, use our FS2004 aircraft compatibility and installation checks for FSX before copying files.
Can FSX and FS2004 run at the same time?
They can technically run simultaneously, but we recommend running only one at a time. Both simulators compete for processor time, memory, sound hardware and controller input, so simultaneous operation can produce stutters, confused joystick responses or unstable add-ons without providing any installation benefit.