It seems as if DVDFab in audiocopy mode generates broken .AVI file containers that are incompatible with Vista's built-in .AVI DirectShow source filter with regard to audio.
Under Vista, DirectShow players (e.g. WMP, Media Center) don't give you any sound when you play DVDFab-generated "audiocopy" .AVI files with an AC3 or DTS soundtrack, although you have installed good DirectShow filters that can handle these audio formats (e.g. AC3Filter, Spdifer or ffdshow). This is applies to the 'generic.avi.h264.audiocopy' and 'generic.avi.xvid.audiocopy' profiles.
The reasons for me to blame DVDFab's AVI file container specifially are:
DS players under XP Plays these .AVIs with both audio and video as long as you have the required DS filters. But presumably Microsoft's .AVI source filter changed between XP and Vista.
Vista still gives you sound on AC3/DTS .AVIs generated with tools other than DVDFab using any DirectShow player as long as you have AC3/DTS DS filters installed. So it's not that Vista with DS can't play AC3/DTS AVIs; it's just DVDFab's AC3/DTS AVIs that are a problem - there's something special about DVDFab's version of the .AVI file container and Vista.
Media Player Classic under Vista plays these .AVIs fine as long as you leave its default setting of using its internal .AVI source filter (under Options->Internal Filters). But the moment you disable that and fallback to Vista's default .AVI source filter, MPC fails to give audio. (On that Options page you can also choose MPC's internal AC3/DTS filter or generic DS filters, and either works as long as you use MPC's .AVI source filter.)
VLC plays these .AVIs since it doesn't depend on DirectShow filters.
Note: This problem may be the same as the problems in this and this thread.