Software & Apps Windows How to Fix D3dx9_40.dll Not Found or Missing Errors A troubleshooting guide for D3dx9_40.dll errors by Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated on October 08, 2019 Windows The Ultimate Laptop Buying Guide Tweet Share Email D3dx9_40.dll problems source from an error with Microsoft DirectX. The d3dx9_40.dll file is one of many files contained in the DirectX software collection. Since DirectX is used 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 FoundThe file d3dx9_40.dll is missingFile d3dx9_40.dll not foundThe 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 uses Microsoft DirectX, but it's most commonly seen in video games. Need for Speed, Gothic, Total War, and Psychonauts are just a few 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 problems. This list includes Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, and Windows 2000. How to Fix D3dx9_40.dll Errors Do not download the d3dx9_40.dll DLL file individually from any "DLL download site." Downloading DLLs from these sites is never a good idea. 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. Restart your computer if you haven't yet. The d3dx9_40.dll error might be a fluke and a simple restart could clear it up completely.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.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 uses DirectX, the software developers will include a copy of DirectX on the installation disc.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.Another example is the GB-ASManager program. When the DLL error is seen there, reinstall the software included on the associated DVD.Sometimes, though not often, the DirectX version included on the disc is a better fit for the program than the latest version available online.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.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.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. 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. 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.