Thanks for getting back to me.
First of all I#m trying to avoid installing any large codecs packs as Win 7 already has a significant pack that allows proper playback - to be honest K-Lite is the one that i would never install (Shark Codecs, maybe yes, but not K-Lite).
I thought somebody would give me more detailed information in regard to the audio - as that's where the problem is I think - wouldn't AC3 filter on its own sort out the thing?
Another question would be in relation to Win 7 native codec settings? Is there any application or option to have a look at these and modify in Win 7?