The Direct X software development kit (SDK) consists of runtime libraries in redistributable binary form, along with accompanying documentation and headers for use in coding.
Originally, the runtimes were only installed by games or explicitly by the user.
Windows XP users who have mistakenly downloaded the latest release can rollback to Direct X 9, which is compatible with their system.
In this article you will learn how to download the latest Direct X release.
Games which don't use the D3DX helpers (such as Source engine games) don't require running the installer on first launch as they only depend on major d3d9/10/11 versions being installed.