I think the OP is saying when they insert the same CD on two different machines, they get different results where launch Setup is only presented on one of the machines.
My guess is it's the Autoplay settings. I don't know which way you want it but try Control Panel->Autoplay and then either
1) Compare Autoplay settings on both machines (to see which way you want it set on both) or
2) Check the use AutoPlay box for all devices (at top) and then check the reset Autoplay defaults box (I think at bottom of window)