DirectX is three different things depending on whether you're a gamer or a developer and what version of Windows you using. DirectX used to be add-on that could be upgraded in older versions of Windows, but in current versions of Windows DirectX is a component of the OS that can't be upgraded. It's also an SDK that developers use to create games that use DirectX. These days when a game installs DirectX it's actually installing part of the DirectX SDK, not DirectX itself, that's meant to redistributed to users. It's always safe to do this. It may end up doing nothing because what it installs is already there, but it will never downgrade the version of DirectX. Since all versions of DirectX are backwards compatible with earlier versions there's also never any need to downgrade.