To play a DirectX 9 game you need the APIs installed and a DirectX 9 capable graphics solution. Same goes for DirectX 10 you need the APIs as well as Path of Exile Orbs
a DirectX 10 capable graphics solution and in fact with DirectX 10, you must be running Vista also.Some people with DirectX 10 capable hardware may choose not run the game with DirectX 10 settings in order to increase their frame rates, as DirectX 10 and 10.1 add extra features and eye-candy to a game which can slow down Cheap Path of Exile Orbs
system performance. So although the APIs are more advanced in DirectX 10/10.1, its not necessarily faster.