OK I figured it out. *Apologise profusley to MC*
You'll like this one.
Last night I had this dilema after watching Underworld,
I'd left my mobile phone back at my parents house.
I use my phone as an alarm clock in the mornings to wake me up.
I was kind of stuck for a while, then I suddenly realised my Cowon D2 player
had an alarm clock on it, although it had no speaker.
So I yoinked the cable for my Amp from my computer out the back, and hooked it up to my
D2. I then ran a quick test and low and behold I had a pretty good sounding stereo alarm clock.
This morning I read Matt's post and go to do a test, but the music (Film) wouldn't play.
I get back this evening to do more testing and notice, that the system claims to be muted,
and won't let me unmute.
It turns out that the soundcard automatically detects whether an audio cable is plugged in,
and if not disables the device.
In disabling the soundcard the DVD Filters won't load for some reason,
and as a result.... the DVD won't play.
Plug the cable back in, the device becomes re-enabled and the DVD filters load,
and instead Vista's copyright protection scheme detects something has change and
refuses to play. (Resolved by a restart I've found in the past)