If you download Microsoft's DirectX End-User Runtime Web Installer, it installs a number of runtime libraries from the legacy DirectX SDK automatically. You may need these to run some video games that use D3DX9, D3DX10, D3DX11, XAudio 2.7, XInput 1.3, XACT, and/or Managed DirectX 1.1. Installing this package won't modify the DirectX Runtime already installed on your PC.