Microsoft Windows DirectX 10 features heavily improved 3D rendering capabilities and several new features to deliver a new generation of visual effects with significantly improved game and 3-D application performance, Sadly, DirectX 10 is officially available for Windows Vista only and Microsoft has no plans to release DirectX 10 for Windows XP, However, guys at "Falling Leaf Systems" ported DirectX 10 on Windows XP starting the project named "Alky" with the aim to provide compatibility libraries for making DirectX 10 work on Windows XP with full support for application development API's, the Alky project is now closed but the source-code is made open-source for further development by community.
The free DirectX 10 compatibility libraries provided by Alky project allow's developers to create DirectX 10 powered games and applications on platforms other than Windows Vista using Microsoft DirectX 10 SDK and API's, Windows XP users on forums and blogs are reporting successfully using Alky's DirectX 10 for Windows XP to port and play Directx 10 only games like Halo 2 and Shadowrun on Windows XP.