Thanks guys, that's really helpful.
The question gets a little more complicated....
My friend has had issues setting Skype up in a way that makes sense and I'd like to avoid the same problems if possible? Not sure if this is hardware related or not?
He uses a Logitech 250 USB headset. Given that he doesn't wear the headset all of the time, it would make sense for the Skype to ring through the main computer speaker (to announce the call). When the call is answered it would make sense for Skype to automatically route the calls audio through the headset (for privacy if nothing else).
It doesn't seem to work that way though. He has to have the main system audio output set to internal speaker (so that he can hear skype ring), and then needs to manually change the pref's to Logitech headset during the call. Is there a way to avoid this problem and make it happen automatically?