DX9 support won’t be coming any time soon. If you need to run a game on WinXP you can use OpenGL. But the good news is DX10 is actually supported by UE4. You can start the editor in DX10 mode by specifying -DX10 or -SM4 at the command line, and then you can actually choose to package your game with DX10 shaders as well as DX11 (which is default) or completely remove DX11 shaders. Under Windows packaging settings.