DirectX 10
This feature is included in the following editions of Windows Vista:
DirectX 10, the latest version of the DirectX suite of multimedia application programming interfaces (APIs), puts gamers and multimedia buffs on the leading edge of PC graphics performance.
DirectX 10 features heavily enhanced 3-D graphics-rendering capabilities and helps noticeably improve your computer's performance in games and high-end 3-D applications. DirectX 10 empowers games to present a new generation of visual effects, and deliver more visual detail per frame than ever before.
Microsoft Flight Simulator X in DirectX 9
Microsoft Flight Simulator X in DirectX 10
Providing a standard 3D development platform for Windows-based PCs, it also provides software developers access to powerful hardware features without the need to write hardware-specific code. For gamers and video enthusiasts, this translates to reliable, higher-performance graphics when you're playing games on your PC.
Check out the official Games for Windows website.