TL;DR: In the Torrent Details : Files view, double-clicking a media file always open the Vuze HD Player, regardless of the setting in Interface : Tables : Launch Helpers. The behavior should be the same as right-clicking : Open, which uses said helpers.

Multiple questions on the forums or here in the suggestion tracker point to this: how to use another media player, instead of the Vuze HD Player. The answer is to use Launch Helpers in Options : Interface : Tables. This works fine, except with media files listed under the torrent details : Files view. Double-clicking them always use the Vuze HD Player. Right-clicking : Open on the item will work as intended however. This should not be the case as the "Open" menu item is emphasized which in UI terms means "default action when activated".

I simply suggest to make the behavior consistent by making double-clicking act the same as right-clicking : Open. As an alternative, another menu item "Open with HD Player" could be added and emphasized so that users know that is the default action, although I don't recommend that since many do not use the HD Player, myself included.

Note that I have no complaints about the Vuze HD Player itself or its continued development. It's simply that it will never offer all the features fully-fledged media players do, nor should it try to as many are either too advanced (like custom renderer settings) or completely outside its scope (like simultaneous playback of an external track).