I've heard the digital output option doesnt work with Vista as of yet. Even the Digital fix made for xp (that sticks the digital output settings after reboots doesnt work for Vista)
I'm trying to find some help on the net, if i do ill post it back here or pm u.
Apparntly SPDIF passthrough forces the use of digital but as of the latest drivers...
SPDIF passthrough is supported on Vista 32-bit only
this is why i dont use vista yet, coupled with my Graphics card, it makes my pc useless.