Vanguard D3dx9

Function
D3dx9_31.Dll is a file that's part of the Microsoft DirectX application. Microsoft DirectX is a program that's primarily used to accelerate the graphical performance for installed graphics cards. D3dx9_31.Dll is especially beneficial for running 3D games. By default, the file is stored in the System32 folder in the Windows directory in Windows Explorer.
Errors
D3dx9_31.Dll errors are usually caused by issues with Microsoft DirectX. If the file is missing or damaged, errors such as the following usually appear on the screen when you try to play Vanguard 3D games: 'File d3dx9_31.dll not found,' 'D3DX9_31.DLL Not Found' or 'The file d3dx9_31.dll is missing.' When you try to start a Vanguard game, the error will automatically pop up on the screen if D3dx9_31.Dll is incapable of executing.
Solution
If you're unable to load Vanguard games, restart your computer to reboot the operating system. If the problem is temporary, a restart solves problems quickly. If that doesn't solve the D3dx9_31.Dll problem, downloading and installing the latest version of Microsoft DirectX is necessary. When you install or reinstall Microsoft DirectX, D3dx9_31.Dll is automatically reinstalled as well. Microsoft DirectX is available directly from the Microsoft website. After installing the program, restart your computer for the changes to take effect.
Warning
There are websites that offer D3dx9_31.Dll as a downloadable file; however, there's no telling whether the files are legitimate or not. If you're running into D3dx9_31.Dll errors, downloading the file from the Internet isn't advisable because you risk downloading malware to your computer.