Can I install multiple copies of FSX on one PC?

Yes, but the only practical way to keep two installer-managed FSX copies on one Windows installation is to install boxed FSX and FSX: Steam Edition side by side. Multiple copies of the same edition are not fully independent because they share Windows profile data and one registered installation path.

Which FSX combinations can run side by side?

Boxed FSX and Steam Edition can coexist; duplicate installations of the same edition cannot be maintained as two fully independent native installs.

FSX Standard and Deluxe are alternative boxed packages, while Gold is Deluxe bundled with Acceleration; they are not separate simulator generations designed for parallel installation. See our comparison of boxed FSX and Steam Edition for the practical differences between the two releases.

Each installed edition still requires legitimate ownership and activation. Copying an installation directory does not create another licence or a separately supported installation.

How do I install boxed FSX and Steam Edition separately?

For the cleanest coexistence setup, install boxed FSX first, run it once, then install FSX: Steam Edition in a different directory.

1. Back up the existing simulator. Preserve the program folder and the FSX data held under AppData, ProgramData and Documents. Our guide to backing up FSX settings, flights and add-ons identifies the locations that a program-folder-only backup misses.
2. Give each edition its own program directory. Never install Steam Edition over the boxed FSX folder or point boxed Setup at Steam's directory.
3. Complete the boxed installation first. Apply only the service packs or Acceleration components appropriate to that boxed copy. Steam Edition already contains the Acceleration functionality, so do not run boxed FSX patches or the boxed Acceleration installer against it.
4. Launch boxed FSX once. This creates its configuration and user-data folders before Steam Edition checks for an existing installation.
5. Install and launch Steam Edition. In a coexistence setup, its profile folders commonly use names such as FSX-SE, while boxed FSX uses FSX. The exact naming can depend on installation history, so confirm folders by their modification times rather than assuming.
6. Direct every add-on to the intended copy. Older installers often read one FSX registry path and may select the wrong edition. Choose the destination manually where possible and check the files before launching FSX. Our aircraft installation guidance for boxed and Steam FSX explains the relevant destination differences.

If Steam Edition was installed before boxed FSX, its profile may already use legacy FSX folder names. Back everything up before changing the arrangement; a clean boxed-first setup is safer than guessing at registry edits or manually renaming profile folders.

Why isn't a copied FSX folder a separate installation?

FSX stores essential state outside its main program directory, so duplicating that directory copies only part of the simulator.

• FSX.cfg, controls and graphics settings are stored under the Windows user profile.
• The active scenery library configuration is normally stored outside the FSX program folder.
• dll.xml and exe.xml control modules and companion programs from profile locations.
• Saved flights, registry paths and some shared add-on data also live elsewhere.

An FSX.exe inside a copied folder may start, but add-on installers, repairs and uninstallers will usually continue targeting the registered installation. Changes made by the clone can also alter the original copy's settings because both executables may read the same profile files.

Can I keep clean and modded FSX setups with one edition?

You can maintain clean and modified states, but a complete known-good backup is more reliable than pretending a copied folder is another installation.

• Back up both the FSX root directory and its external configuration locations before adding aircraft, scenery or modules.
• Disable optional scenery through the Scenery Library when testing rather than repeatedly reinstalling it.
• Keep downloaded packages and their documentation outside the live FSX directory so an add-on can be restored or removed cleanly.
• Use separate Windows accounts only when different controls and user settings are the goal. Accounts separate some AppData and Documents files, but they do not create separate program installations or isolate all machine-wide data.

For the strongest native separation, use boxed FSX as one environment and Steam Edition as the other. For occasional testing, one installation plus a full backup introduces fewer registry and add-on detection problems.

What commonly goes wrong with two FSX installations?

The most common failure is an add-on silently installing into the other FSX copy.

• Missing aircraft or scenery: inspect the destination selected by the installer and confirm which edition was launched.
• Both editions inherit the same settings: check which AppData folder changes when each simulator closes; the installations may be sharing a profile.
• Modules fail or load twice: inspect the appropriate dll.xml and exe.xml rather than copying those files wholesale between editions.
• Steam files become damaged after patching: remove any boxed service pack or Acceleration files applied to Steam Edition and use Steam's file verification facility.

Avoid registry-cleaning utilities and manual path edits unless you have a verified backup. FSX add-on installers depend heavily on those paths, and changing one to fix a single package can redirect every installer that follows.