Fix an FSX reinstall blocked by an old installation. Remove boxed or Steam leftovers safely, clear stale paths, and preserve add-ons.
Microsoft Flight Simulator X (FSX) usually refuses to reinstall because Windows Installer still records the boxed edition, Steam leaves non-Steam add-on files, or an old FSX registry path survived an incomplete uninstall. Remove the edition through its own uninstaller first, back up wanted add-ons, delete only confirmed leftovers, restart Windows, then reinstall cleanly.
Why does FSX still think it is installed?
Deleting the FSX folder does not remove its Windows Installer registration or registry paths. This is the mistake we see most often: the executable has gone, but Setup still finds enough installation data to enter maintenance mode, report that FSX is already installed, or select an obsolete directory.
| Symptom | Likely cause | Best next step |
|---|---|---|
| Setup offers Repair or Remove | The boxed edition remains registered | Choose Remove before deleting folders |
| FSX remains in Installed apps | Broken Windows Installer entry | Repair the entry with the original installer, then uninstall it |
| Setup or an add-on selects an old folder | Stale FSX registry path | Check the edition-specific registry entries |
| Steam reinstalls but old modifications return | Unmanaged add-on and configuration files remain | Remove or rename the residual FSX folders |
What should I back up before removing FSX?
Back up only material you recognise and want to keep. Typical items include third-party aircraft, scenery, effects, gauges, saved flights, controller assignments and add-on licence information.
Do not plan to copy the entire old installation over the new one. That can restore the damaged file, incompatible module or altered configuration that caused the reinstall. Keep the backup as a reference and restore add-ons individually after stock FSX works.
How do I remove the old FSX installation?
- Identify the installed edition. Boxed FSX and FSX: Steam Edition use different uninstall methods and can leave different registry records. If both have been installed, do not assume every folder named FSX belongs to the edition being removed.
- Uninstall major add-ons first. Remove scenery packages, weather engines, traffic tools and aircraft that have their own uninstallers while their installation records still point to FSX.
- Remove boxed FSX normally. Open Windows Installed apps or Programs and Features. If FSX Acceleration is listed, remove it before the base simulator, then uninstall Microsoft Flight Simulator X. If the entry is broken, run the matching original Setup programme and use its Remove or Repair option.
- Remove FSX: Steam Edition through Steam. Use the Steam client’s uninstall command rather than the boxed FSX installer. Steam removes managed files but may leave files installed by third-party add-ons.
- Restart Windows. This releases files and installer services that may still be in use.
- Inspect the old simulator directory. Common defaults are
C:\Program Files (x86)\Microsoft Games\Microsoft Flight Simulator Xfor boxed FSX andC:\Program Files (x86)\Steam\steamapps\common\FSXfor Steam. A Steam library or custom boxed installation may be on another drive. Delete only the FSX directory after confirming that the backup contains anything needed. - Reset user configuration files. Inspect
%APPDATA%\Microsoft\FSX,%PROGRAMDATA%\Microsoft\FSXand%USERPROFILE%\Documents\Flight Simulator X Files. Rename wanted configuration folders first, such as by adding.old, rather than permanently deleting them. Folder and file names can differ when boxed and Steam editions have coexisted.
Never delete C:\Windows\Installer, an entire Steam library, or broad Microsoft registry branches. Our detailed FSX clean-removal procedure covers the remaining folders and backup decisions without risking unrelated software.
What if FSX Setup still detects the old installation?
A reinstall that remains blocked after file removal usually has a stale installer record or registry path. Start the original boxed installer again and use Repair followed by Remove if those options are available; Windows’ programme installation troubleshooter can also clear an uninstall entry that no longer works.
If FSX has disappeared from the installed-programmes list but Setup or add-on installers still find it, follow our edition-specific FSX registry repair steps. Export any key before changing it, and do not use a general registry cleaner. Boxed FSX and Steam Edition should not be forced to share an installation path.
An 1607 message points to the legacy InstallShield system or Windows permissions rather than residual aircraft and scenery files. Use the targeted fixes for FSX error 1607 instead of repeatedly deleting the simulator directory.
Reinstalling without bringing the problem back
Install the same FSX edition using its proper installer: original media or installer for boxed FSX, and the Steam client for FSX: Steam Edition. Run the boxed installer with administrator rights. A simple custom directory outside protected Windows programme folders can reduce permission trouble with older add-ons, while Steam should remain inside a configured Steam library.
Launch the unmodified simulator once before installing anything else. Confirm that a default aircraft loads at a default airport, close FSX normally, and then add scenery, aircraft and utilities one category at a time. Do not immediately restore old copies of FSX.cfg, dll.xml or scenery.cfg.
If an older add-on keeps detecting boxed FSX instead of Steam Edition, the issue is usually its expected registry path rather than the simulator download itself. Our boxed-versus-Steam add-on compatibility guidance explains how to distinguish an installer-detection problem from a genuinely incompatible add-on.