Requirement: 64-bit Intel CPU, Mac OS X 10.7 or later.
dir C:\Windows\System32\d3dx9*.dll
The safest way to get these "extra files" is through official Microsoft installers rather than third-party sites: Web Installer: DirectX End-User Runtime Web Installer
Many texture mods for DX9 games (ENB Series, SweetFX) require d3d9.dll proxies. If you are using a custom d3d9.dll in your game folder, the system ignores the system files. Ensure your mod loads the correct architecture version.
Modern Windows includes the core DirectX 9.0c runtime, but not the optional "side-by-side" components like XAudio 2.7 XInput 1.3 Architecture: