This DirectX 10 for windows XP still in alpha stages and isn’t the original of DirectX 10 files from Microsoft. As Microsoft has announced that the DirectX 10 currently support to Windows Vista only.This line is not shown in the main page
However, Cody Brocious the Alky Project leader has released a full preview of DirectX 10 Alky preview compatibility libraries for Microsoft DirectX 10 enabled games. These compatibility libraries allow the use of DirectX 10 games on platforms other than Windows Vista , and increase hardware compatibility even on Vista, by compiling Geometry Shaders down to native machine code for execution where hardware isn’t capable of running it. No reason for gamer to change or upgrade the OS and video card(s) to play the latest games.
Here are 2 pictures sample to difference’s from DirectX 9 and DirectX 10 on images quality.
DX 9 scenery from Flight Simulator X


A rendering of the same scenery with DirectX 10



Here is the latest DirectX 10 for Windows XP ( Click to download ) which can be used with DX10 SDK.