There is an buildin DX3 in NT4.U can't install any other version DX onto NT4,so please give up to seeking the DX5 NT version.
Maybe you will ask :AOE which need DX5,but it still can be played on NT4,why.
reason here:
such game only use high vesion of DINPUT,which exist higher version for NT,but for the main part of DX(DDRAW & D3D),DX3 is the only available version for NT,no higher and no lower.
for 2000,it is said that will be an build in DX7,but according to my test,most of teh driver doesn't work properly now under DX7 for 2000,while DX6 driver works perfectly.