If you are looking for groundbreaking graphics technology then opt in for Windows Vista Operating System which comes with preinstalled DirectX 10 for the highest gaming performance by enhancing the details and offering you with a better experiance. Though most of the games currently available are written for DirectX 9 but the new upcoming games are all optimized for DirectX 10 and hence you either need to upgrade to Windows Vista or else download DirectX10 for Windows XP.
Game run on DirectX 9 – Game run on DirectX 10
Download DirectX 10.0 and 10.1 for Windows XP :
Copy d3d10.dll, d3dx10.dll, d3dx10.dll, dxgi.dll, and Nucleus.dll to C:\windows\system32\
Download Link for DirectX 10