Make and model and any other specs from the label on the fan you removed from the PSU?
Make and full model no. and any other specs from the label of the new fan?
Make and full model no. of PSU?
I've not seen a fan with an orange lead. Many have yellow for the speed sensor wire (I've also seen blue or white). Power wires are usually red and black. Red is +12 and black is ground. If you are using the same two pins inside the PSU, the fan might not work if it is not the same or very close to the same internal resistance as the fan that was removed because the thermal control circuit is matched to the power needs of that fan.
So if you wan't to use that fan, you may have to bring the fan lead outside the PSU case (may need an extension or two) and hook it to your fan controller or a header on the mobo.
.bh.