By Delia / Last update March 29, 2022

The d3dx9_40.dll file is part of the Microsoft DirectX Software Distribution Kit, the d3dx9_40.dll issue stems from a Microsoft DirectX error. Like any other DLL (Dynamic Link Library) file, d3dx9_40.dll also contains certain functions that can be called by other third-party applications, which allows multiple software and games to share functionality that is rooted in a single file. Since most Windows-based games and advanced graphics programs use this software, the d3dx9_40.dll error usually occurs only when using these programs.

Any Microsoft operating system since Windows 98 can be affected by d3dx9_40.dll and other DirectX issues. This includes Windows 11, Windows 10, etc. In this guide, we will try to fix it using various possible solutions.

d3dx9_40.dll not found error

Possible d3dx9_40.dll error message

Error messages related to d3dx9_40.dll may appear in any program that uses Microsoft DirectX, but it is most common in video games. You may encounter:

  • The file d3dx9_40.dll is missing
  • File d3dx9_40.dll not found
  • The program can't start because d3dx9_40.dll is missing from your computer
  • This application failed to start because d3dx9_40.dll was not found
  • D3dx9_40.dll not found. Reinstalling might help fix this
  • The code execution cannot proceed because d3dx9_40.dll was not found
  • C:\Windows\system32\d3dx9_40.dll is either not designed to run on Windows or it contains an error...

Although the error messages are different from each other, in most cases the main reason is the same - d3dx9_40.dll is corrupted or missing from your system.

How to fix d3dx9_40.dll missing or not found

First, you can try restarting your computer once. If the d3dx9_40.dll error is occasional, a simple restart might fix it. In addition, you can also try to install the latest version of Microsoft DirectX, uninstall and reinstall the problematic software, update the driver, etc.

Note: Please avoid downloading and replacing the d3dx9_40.dll file from third-party sources as they may inject viruses or malware into your system.

Way 1. Install the latest version of Microsoft DirectX

First, you should try to download and install the latest version of Microsoft DirectX. This method has proven to fix many errors for affected users and may work for you as well. So, search for DirectX in the Microsoft Download Center and download the latest version of DirectX End-User Runtime Web Installer. after that, run the installer and follow the on-screen instructions to complete the DirectX installation. Then, restart your PC and check if the error is now fixed.

Download link:

download microsoft diretx

If this does not fix the problem, there may be some underlying corruption that you need to deal with.

Way 2. Uninstall and reinstall the problematic software

In some cases, the problem is with the wrong software or game itself. You may receive this error because the program was installed incorrectly or the installation files associated with the software are corrupt. If the previous method did not work, you should try uninstalling and then reinstalling the problematic software to see if the error is fixed.

First, open the Settings app by pressing Win + I hotkeys, then go to the Apps > Apps & features section and find the problematic software from the list of installed applications. Select the three-dot menu button next to the software and click the Uninstall option. Follow the instructions to complete the uninstallation of the software.

apps features uninstall

Then, download the latest version of the software or game from the official website to see if the error is fixed.

Way 3. Update the graphics card driver

If none of the troubleshooting tips work, then the problem may be with your drivers. Outdated graphics card drivers sometimes cause errors when playing newly released games, so this could be the cause of it. However, before updating your drivers, check that the driver update does not cause further errors. Sometimes, driver updates cause more problems than they solve, so make sure you are not causing further damage.

update graphic card driver

Way 4. Delete the corrupted d3dx9_40.dll

If none of the above solutions work for you, you can try another fix. You can replace the corrupted d3dx9_40.dll file with a new copy. The error most likely occurred due to some underlying corruption. Therefore, in this case you should be able to fix it by recovering the good d3dx9_40.dll file on your system.

To replace the DLL file in question, we will first delete the file and then restore it from the latest DirectX package. If deletion is not allowed, you can try renaming the file. Let's see the process of recovering the d3dx9_40.dll file.

First, use Windows + E hotkey to open File Explorer and find d3dx9_40.dll file in this location: C:\Windows\System32

Next, select the d3dx9_40.dll file and delete it. If deleting the file shows a different error or you are unable to delete it, you can try renaming the file using the .old extension.

After that, go to the C:\Windows\SysWOW64 in File Explorer and repeat the above process for the d3dx9_40.dll file.

Then, download the DirectX End-User Runtimes (latest version) installer from the official source, start the installer, and follow the on-screen instructions to complete the installation. This will restore the missing d3dx9_40.dll file.

Finally, restart your computer and then check if the error is now fixed.