I have noticed a lot of aftermarket flight simulation AddOn installers that only natively support maybe one or two versions of the popular platforms out there. These AddOns include everything from aircraft, terrain, airports, weather, services, scenery, navigation, and more. For example, they may support Microsoft Flight Simulator X (FSX), but not Lockheed Martin Prepar3D (P3D) or Dovetail Games FSX Steam Edition (FSX:SE). Or, they support P3Dv2, but not P3Dv3.

While this is up to the developer to offer, I wanted my existing AddOns to work with my older platform, P3Dv3 (not P3Dv4). Ultimately, it is possible for every one I tried. I found that, in order to make these AddOns think that specific flight simulation software is installed, I needed to modify the Windows Registry. In certain cases, I also needed to create dummy files. This post is about how I solved getting various versions to work with my own system.

WARNING! Misuse of the Windows Registry can ruin your entire Windows operating system. You should learn how to reliably use the Registry Editor first. If you are not comfortable with this, STOP HERE AND DO NOT ATTEMPT THIS! my737ng.com can not be held responsible for your own actions.

NOTE: These steps were performed on 64-bit Windows 7 and 10 operating systems with a single user account. If using another Windows versions or accounts, the procedures and results may be different.

INSTALLING FSX ADDONs INTO P3D v2/v3

On my test machine, I do not have FSX, but I do have P3D v3 installed. To make my FSX AddOns think my P3D is actually an FSX installation, I started with the Windows Registry Editor:

• Create the missing FSX keys
  • HKEY_CURRENT_USER\Software\Microsoft\Microsoft Games\Flight Simulator\10.0
• Create a String Value called AppPath and set the value to the directory where your Prepar3D.exe main application is. In my case, it is E:\P3Dv3\ and be sure to include the \ at the end.

• Create the missing FSX keys (may be needed)
  • HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Microsoft Games\Flight Simulator\10.0
• Create a String Value called SetupPath and set the value to the directory where your P3D.exe is. In my case, it is E:\P3Dv3\ and be sure to include the \ at the end.

• Then, I created a blank text file and saved it as FSX.exe in my P3Dv3 directory alongside the existing Prepar3D.exe application. Only some AddOns check for the existence of this file, but better to just put it in there to be sure.

NOTE: Prepar3D v3 does not natively create or use the <P3D root directory>/Addon Scenery folder that FSX used. You may have to add some add-ons to the Scenery Library manually if they end up in this folder.

FSX-specific AddOns should now think your P3D v2/v3 is a valid FSX and install correctly. P3D v2/v3 capable FSX AddOns will see both simulators as installed, but accomplish the same by selecting either choice (do not select both).

INSTALLING P3Dv2 ADDONs INTO P3Dv3

Some AddOns have not been updated for P3Dv3 yet, but work with P3Dv2. The only real difference between P3D version 2 and P3D version 3, with regards to AddOns, is some added Windows Registry settings:

• Create the first missing P3D v2 key
  • HKEY_CURRENT_USER\Software\Lockheed Martin\Prepar3d v2
• Create a String Value called AppPath and set the value to the directory where your version 3 Prepar3D.exe application is. In my case, it is E:\P3Dv3\ and be sure to include the \ at the end.
• Create a DWORD Value called Installed and set the value to 1

• Create the second missing P3D v2 key (may be needed)
  • HKEY_LOCAL_MACHINE\Software\Wow6432Node\Lockheed Martin\Prepar3d v2
• Create a String Value called SetupPath and set the value to the directory where your version 3 Prepar3D.exe application is. In my case, it is E:\P3Dv3\ and be sure to include the \ at the end.

NOTE: Prepar3D v3 does not natively create or use the <P3D root directory>/Addon Scenery folder that P3Dv2 used. You may have to add some add-ons to the Scenery Library manually if they end up in this folder.

That should do it. No dummy files are needed as the Prepar3D.exe application does not change names between versions 2 and 3.

INSTALLING FSX ADDONs INTO FSX:SE

If you never had FSX installed, then FSX:SE will use the normal FSX folder structure and names. All normal FSX AddOns should install fine.

However, if you already have FSX installed, FSX:SE will create a “dual installation”. To install FSX AddOns that do not support FSX:SE, you need to temporarily change some Windows Registry keys to re-point at the Steam Edition.

NOTE: I have never used FSX:SE, so the following is based on information I was able to uncover online. Use at your own risk!

• Create the missing boxed FSX keys
  • HKEY_CURRENT_USER\Software\Microsoft\Microsoft Games\Flight Simulator\10.0
• Create a String Value called AppPath and set the value to the directory where your FSX:SE is. By default, this is C:\Program Files (x86)\Steam\steamapps\common\FSX\ and be sure to include the \ at the end.

• Create the missing boxed FSX keys (may be needed)
  • HKEY_LOCAL_MACHINE\Software\Wow6432Node\Microsoft\Microsoft Games\Flight Simulator\10.0
• Create a String Value called SetupPath and set the value to the directory where your FSX:SE is. By default, this is C:\Program Files (x86)\Steam\steamapps\common\FSX\ and be sure to include the \ at the end.

At this point, for those with dual-installations, normal FSX installers should see the FSX:SE installation as default FSX. If you want to install something back into normal FSX, you will need to change these back.

Thanks for being a visitor and I hope this helps others!

FSX imagery by Microsoft Games, Inc. Prepar3D imagery by the Lockheed Martin Corporation. FSX Steam Edition imagery by Dovetail Games. Header image icons sourced from Freepik at Flaticon. my737NG.com is not affiliated with, maintained, authorized, endorsed, or sponsored by any of these companies.