[Five]

I was thinking that gspot would do it

I'm not too expert in DVD matters

if you can manage to extract some audio from the DVD and post up a little sample to rapidshare or similar I can take a look at it here to tell you if its stereo or mono (or even mono captured as stereo but slightly imbalanced).

you could also listen to it on headphones, if there's some part where something is obviously coming from the right or left only then its gotta be stereo.

hopefully some of the heavyweight video guys will stumble in here with an easier method.