Oops... I just solved my previous message. In XP the Realtek audio drivers don't give you a separate "Realtek digital output" - instead the standard "Realtek HD Audio" is routed to Optical whenever the plug is inserted. This is better on several fronts than Vista: -The output remains active so there's no pause before playing anything due to the reciever waking up (this is why I didn't notice it working!) -It's always on full volume so you can leave a volume on the reciever and find it the same the next time you use it. -It's on the same output so no having to close your app, change the audio output in Control Panel, then reopen it!! This was a pain in the neck in Vista. Working fine on the latest R221 drivers from Realtek (I get a blanked out "SPDIF" slider in my mixers). Like others I initially found that with the R171 driver the jack didn't work.