hi i think that WindowsXP-KB839643-x86-ENU.EXE is for the directx version that originaly comes with xp (directx 9) and DirectX90-KB839643-x86-ENU.EXE is for a different version of directx (directx 9a ,9b) thats why you can't install the first and the second should be in an unattended install (together with 9b of course)