How to Fix D3dx9_40.dll Not Found or Missing Errors

A Troubleshooting Guide for D3dx9_40.dll Errors

D3dx9_40.dll Error
D3dx9_40.dll Error.

D3dx9_40.dll issues are caused in one way or another by an issue with Microsoft DirectX.

The d3dx9_40.dll file is one of many files contained in the DirectX software collection. Since DirectX is utilized by most Windows based games and advanced graphics programs, d3dx9_40.dll errors usually show up only when using these programs.

There are several ways that d3dx9_40.dll errors can reveal themselves on your computer. Here are several of the more common specific d3dx9_40.dll error messages:

D3DX9_40.DLL Not Found
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. Try reinstalling the program to fix this problem.
D3dx9_40.dll not found. Reinstalling might help fix this

The d3dx9_40.dll error message could apply to any program that utilizes Microsoft DirectX, but it's most commonly seen related to video games.

Need for Speed, Gothic, Total War, and Psychonauts are just a couple examples of games that have been known to generate d3dx9_40.dll errors.

Any of Microsoft's operating systems since Windows 98 might be affected by d3dx9_40.dll and other DirectX issues. This includes Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, and Windows 2000.

How to Fix D3dx9_40.dll Errors

Important Note: Do not download the d3dx9_40.dll DLL file individually from any "DLL download site". There are a number of different reasons that downloading DLLs from these sites is never a good idea.

Note: If you've already downloaded d3dx9_40.dll from one of those DLL download sites, remove it from wherever you put it and continue with these steps.

  1. Restart your computer if you haven't yet.
    1. The d3dx9_40.dll error might be a fluke and a simple restart could clear it up completely.
  2. Install the latest version of Microsoft DirectX. Chances are, upgrading to the latest version of DirectX will fix the d3dx9_40.dll not found error.
    1. Note: Microsoft often releases updates to DirectX without updating the version number or letter so be sure to install the latest release even if your version is technically the same.
    2. Note: The same DirectX installation program works with all versions of Windows including Windows 10, 8, 7, Vista, and XP. It will replace any missing DirectX 11, DirectX 10, or DirectX 9 file.
  3. Assuming the latest DirectX version from Microsoft doesn't fix the d3dx9_40.dll error you're receiving, look for a DirectX installation program on your game or application CD or DVD. Usually, if a game or​ another program utilizes DirectX, the software developers will include a copy of DirectX on the installation disc.
    1. For example, if you're using the game with Steam, it's probably called DXSETUP.exe, and can be found in a redist folder in the game's installation directory. If you can't find it manually, try searching your entire computer for "dxsetup.exe" using a file search tool like Everything.
    2. Another example is the GB-ASManager program. When the DLL error is seen there, it's advised to reinstall the software included on the associated DVD.
    3. Sometimes, though not often, the DirectX version included on the disc is a better fit for the program than the latest version available online.
  1. Uninstall the game or software program and then reinstall it again. Something might have happened to the files in the program that work with d3dx9_40.dll, and a reinstall could do the trick.
  2. Restore the d3dx9_40.dll file from the latest DirectX package. If the above troubleshooting steps haven't worked to solve your d3dx9_40.dll error, try extracting the d3dx9_40.dll file individually from the DirectX package.
  3. Update the drivers for your video card. While it's not the most common solution, in some situations updating the drivers for the video card in your computer could correct this DirectX issue.

Need More Help?

See Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more. Be sure to let me know the exact d3dx9_40.dll error message that you're receiving and what steps, if any, you've already taken to resolve it.

If you're not interested in fixing this problem yourself, even with help, see How Do I Get My Computer Fixed? for a full list of your support options, plus help with everything along the way like figuring out repair costs, getting your files off, choosing a repair service, and a whole lot more.