DirectX is Microsoft's API for games, a pretty nice way of saying that DirectX lets game developers easily take advantage of the latest developments in graphics technology. And, if you want the game to look the finest, you'll need DirectX 10 hardware that will thrust four times the velocity of processing-rate.

However, to take advantage of DirectX 10, you'll also need Windows Vista, the anticipated successor to Windows XP. According to Microsoft, DirectX 10 will be able to display graphics up to 8 times more quickly than DirectX 9.0c. It means not that it would raise the ultimate score by four times.
Via: theinquirer