If you have obtained this specific legacy installer, follow these steps for a pristine installation:
Even in its original release state, v4.0.23.21468 looks stunning. Here are the optimal settings for balancing visual quality and performance: Prepar3D v4 Professional Plus 4.0.23.21468
For Professional Plus users, ensure "Detailed Military Textures" is toggled ON in the Display settings. This enables the proper rendering of military liveries and weapon pylons. If you have obtained this specific legacy installer,
With Prepar3D v6 and v7 now available, you might ask why anyone would install 4.0.23.21468. The answer lies in compatibility and stability. For Professional Plus users
Many legacy add-ons—specifically military-grade simulations from companies like Milviz, A2A Simulations, and VRS (Vertical Reality Simulations)—were built specifically for the v4.0 SDK. These developers have gone defunct or have not updated their products to v5/v6. For a museum flight simulator, a university aerospace lab, or a collector of classic simulation software, v4.0.23.21468 is the final "gold standard" version where everything just works without DRM license server issues.
Furthermore, because v4.0.23.21468 lacks the "TrueSky" volumetric cloud engine found in v5, it runs significantly better on older hardware (GTX 970/GTX 1060 tier). For flight schools on a budget, this build allows 30+ frames per second on tri-screen setups where v5 struggles to hit 15.