Here is a response that Chuck Walbourn of Microsoft posted in the
vista.games section on April 16th 2007
"Technical clarification: Windows Vista's runtime supports Direct3D9,
Direct3D9Ex, Direct3D10, and older interfaces. DXDiag reports it as "version
10" for simplicity, but that number has been meaningless for a few years
now. The Windows Vista runtime also supports all the other usual DirectX
9.0c interfaces except DirectPlay Voice and Direct3D Retained Mode which
were removed. When you run the DirectX End-User Runtime installer or a game
uses the DirectSetup REDIST on Windows Vista (or XP SP 2 for that matter)
nothing in the runtime gets updated or installed. Only the SDK optional
components like D3DX9, D3DX10, XACT, XINPUT, etc. get installed.
The new Aero desktop uses Direct3D9Ex. This API requires Windows Vista, a
DX9 card, and a WDDM driver. It does NOT require Direct3D 10.
The Direct3D 10 API requires Windows Vista and a Direct3D 10 video card. No
released game creates a Direct3D 10 device at this time, although a number
of them have been announced as coming in future products and/or patches"
Here is a snapshot of trying to run a game like Fear, before installing the
DirectSetup REDIST
http://images1.filecloud.com/431143/missing_DX_file.jpg
You get the same error message if you try to run Fear under XP.
Apply any of the runtime updates, and the error goes away and the game works
fine. Chuck advises against, going out to the web and grabbing just the one
file. Not it points you to the DX runtime files
From his April 9th post in Vista.games
"You should never download system components from random websites and drop
them on your system unless you know they come from a reliable source. That's
a fast way to get hacked. If you are missing any version of D3DX due to a
failed or badly desigend installer, run the DirectX End-User Runtime
Installer on the Microsoft site and it will install all the supporting SDK
components we've released. Got to
http://www.microsoft.com/directx/ and
follow the link for "Get the Latest DirectX Here"