How do I repair missing or corrupted FSX files?

To repair missing or corrupted FSX files, first back up any modified stock files and add-ons. In FSX: Steam Edition, verify the installation through Steam. For boxed FSX, run Repair from the original discs or Windows' installed-programs panel, then repair Acceleration or reapply the service packs if needed.

Which FSX repair method should I use?

Use the repair method that matches your FSX edition; boxed and Steam files are not interchangeable.

Both methods can replace missing or altered official executables, libraries, gauges, textures, scenery and default aircraft files. They cannot restore a third-party gauge or dependency that was never part of FSX.

What should I back up before repairing FSX?

Back up anything you have added to or modified inside the FSX installation folder, especially changes made directly to stock content.

• Modified aircraft.cfg, panel, texture and model files
• Custom gauges, effects, sounds and scenery
• Add-on aircraft and AI packages installed inside the FSX folders
• dll.xml, exe.xml, scenery.cfg and fsx.cfg
• Saved flights, control assignments and any add-on licence information

A mistake we see often is restoring the entire old FSX folder after a successful repair. That can put the corrupted or obsolete file straight back. Restore only the add-ons and modifications you actually need, preferably one package at a time.

How do I repair FSX: Steam Edition files?

Steam's Verify integrity of game files function compares installed FSX files with its official copies and downloads replacements where necessary.

1. Close FSX and any utilities that use its files.
2. Open the Steam Library, right-click Microsoft Flight Simulator X: Steam Edition and select Properties.
3. Open Installed Files and select Verify integrity of game files. In older Steam layouts, the command may appear under Local Files.
4. Allow replacement files to download, then restart Steam if it requests it.
5. Launch FSX with a stock aircraft and airport before reinstalling or restoring any modifications.

Verification normally leaves extra third-party files in place, but it can overwrite an add-on's changes to official files. That includes edited default aircraft, replacement textures and modified stock gauges. Reinstall the affected add-on afterwards rather than copying back the whole backup.

Do not copy boxed-edition executables or DLL files into Steam Edition, and do not download individual replacement DLLs from an unknown source. Use Steam's official copies.

How do I repair boxed FSX from the discs?

The boxed installer can restore original FSX files, but the installation layers must be repaired in the correct order.

1. Close FSX and back up your add-ons and modified stock files.
2. Open Programs and Features in Windows, select Microsoft Flight Simulator X and look for the Change or Repair option. If it is unavailable, insert FSX Disc 1, run setup.exe and choose Repair.
3. Complete the base FSX repair using media that matches the installed edition.
4. Restore the update layer. If Acceleration is installed, run its installer and repair or reinstall it after repairing base FSX. Without Acceleration, reapply the official service packs previously used by that installation.
5. Start FSX once with no add-ons enabled, confirm that stock content works, then restore add-ons gradually.

Repairing base FSX after Acceleration can replace newer files with older base versions, which is why Acceleration must be handled afterwards. FSX Gold also uses separate base and Acceleration installation layers.

If the boxed installer cannot detect FSX or points to an obsolete folder, address the broken FSX installation path in the Windows registry before attempting another repair. Do not manually copy registry entries from another computer.

Why are files still missing after an FSX repair?

If official files remain missing after a successful repair, either something is removing them again or the reported problem is outside the core FSX installation.

• Security software quarantined the file: review its quarantine history and confirm that the file came from Steam or the original FSX media. Do not permanently disable protection.
• The add-on uses the wrong FSX folder: boxed FSX and Steam Edition can exist at different paths, and an installer may have written files into an old installation.
• The missing item belongs to an add-on: repair or reinstall that add-on. FSX verification has no reference copy for third-party aircraft, gauges or scenery.
• Windows blocks replacement files: an access-denied error indicates a permissions problem rather than file corruption. Our explanation of what ResetXDirectorySecurity changes in FSX covers when the supplied permissions tool is appropriate.
• The configuration is corrupt: close FSX and rename fsx.cfg, then let the simulator generate a fresh one. It is normally under %APPDATA%\Microsoft\FSX or %APPDATA%\Microsoft\FSX-SE; Steam Edition can use either name depending on installation history.

If the symptom is a crash rather than a named missing file, replacing the installation may not help. Use a symptom-based FSX crash diagnosis to separate core-file damage from scenery, gauges, modules and configuration faults.

When should I reinstall FSX completely?

Reinstall FSX only when verification or Repair repeatedly fails, the installation is split between obsolete folders, or damaged extra files remain after the official files have been restored.

Back up user content first. After uninstalling, rename any remaining FSX installation folder instead of immediately copying it into the new installation; uninstallers often leave third-party DLLs, gauges and scenery behind. Install and test base FSX, apply Acceleration or the required service packs, test again, and only then add third-party content in small groups.