How do I perform a clean reinstall of FS2004?

To perform a clean reinstall of Microsoft Flight Simulator 2004 (FS2004/FS9), back up only irreplaceable user files, uninstall add-ons and the simulator, remove or rename remaining FS9 folders and configuration data, reboot, reinstall into a fresh folder, apply the FS9.1 update, test the stock simulator, then restore add-ons individually.

A clean reinstall is different from copying the old installation back over a new one. Its purpose is to eliminate damaged configuration files, incompatible modules, abandoned scenery entries and other leftovers that can survive a normal uninstall.

What should I back up before reinstalling FS2004?

Back up personal content and installers, but keep them separate from the new installation until FS2004 has passed a stock test.

• Saved flights, flight plans, screenshots and logbook data you want to retain.
• Original repaints, aircraft, scenery or panel work that cannot be downloaded or recreated.
• Add-on installers, licence details and a written list of installed products.
• Your existing fs9.cfg for reference only, especially if you need to recreate controller assignments or graphics settings.

On modern Windows, FS9 configuration data is normally under %APPDATA%\Microsoft\FS9, while saved flights are commonly under Documents\Flight Simulator Files. Do not immediately restore the old fs9.cfg or scenery.cfg; either one can reintroduce the fault you are trying to remove.

FS2004 clean reinstall steps

1. Uninstall add-ons first. Use their original uninstallers while the FS2004 installation path still exists. This is particularly helpful for scenery, utilities and products that place files outside the main simulator folder.
2. Uninstall FS2004. Use Windows Programs and Features, Installed apps, or the removal option provided by the original FS2004 media.
3. Inspect the old installation folder. If it remains, rename it rather than deleting it immediately—for example, change Flight Simulator 9 to Flight Simulator 9.old. This preserves recoverable personal files without letting the installer reuse them.
4. Reset user configuration data. Rename the FS9 folder under %APPDATA%\Microsoft. Also check Windows VirtualStore for an FS2004 mirror if the simulator was previously installed under Program Files.
5. Remove stubborn remnants only when necessary. Registry editing is normally needed only when Setup still believes FS2004 is installed or the uninstall entry is broken. Our detailed FS2004 removal procedure covers the remaining folders, shortcuts and simulator-specific registry entries. Avoid general-purpose registry cleaners.
6. Restart Windows. This releases locked files and completes pending uninstall operations.
7. Install into a new writable folder. On Windows 10 or 11, a path such as C:\Games\FS2004 usually avoids the permissions and VirtualStore complications associated with Program Files. Our modern-Windows installation guidance explains the recommended location and first-launch checks.
8. Launch the unmodified simulator once. Allow FS2004 to create a fresh configuration, load a default aircraft at a default airport, then close it normally. Do not add scenery or replace aircraft yet.
9. Apply the official FS9.1 update. Follow the correct FS2004 patch and testing order, then launch the simulator again before installing anything else.
10. Restore add-ons gradually. Install from the original packages where possible and test FS2004 after each add-on or small group.

How should I restore FS2004 add-ons?

Restore add-ons in controlled stages so that the first failure identifies the likely cause.

• Begin with essential modules and hardware utilities that explicitly support FS2004.
• Add scenery in small groups, checking both the Scenery Library and a flight at the affected airport.
• Install aircraft through their original packages so shared gauges, sounds and effects go to the correct locations.
• Restore AI traffic, weather programs and other background utilities last.

A mistake we see constantly is copying the entire old Flight Simulator 9 directory over the clean installation. That also copies obsolete modules, duplicate gauges, modified default files and damaged scenery references, effectively undoing the reinstall.

Why does FS2004 still fail after a clean reinstall?

If untouched FS2004 still crashes or refuses to launch, the old add-ons were probably not the cause.

• Confirm that Windows created a genuinely new fs9.cfg rather than reusing the old profile.
• Check that the installation folder is writable and is not being redirected through VirtualStore.
• Test before enabling compatibility settings; apply them only to solve a specific problem.
• Remember that original disc-launch protection can cause problems on newer Windows versions even when installation succeeds.
• Verify that the failure occurs with a default aircraft, airport and flight.

For faults that remain at that stage, use our FS2004 checks for Windows 10 and 11 rather than repeating the reinstall or restoring old files.