[BTM] Imac does not seem to recognize device in USB

[Jan Rutgers]

L.s,
I have put an externel BT-thing in the USB. It is shown in the hardware
"about this apple" but the bluetooth icon is not shown in the
systempreferences. When I search it it says it is hidden beause there is no
internal or external BT-module. Does anybody know how to make this work?
P.s I have an Imac OS 10.4

Thanks,Jan Rutgers, Amsterdam.