I geeked and I found it. The primary reason why I wasn’t able to get the audio stream was because DVD2AVI is no longer developed and pretty old. It’s successor is: dgmpgdec156. To make a long story short I managed to get an AAC file from the project save done on this tool based on the old DVD2AVI. AAC can be played by my winamp and thus it can be written to disk as WAV. Hence, I could encode the two together in virtualdub as usual. I will make an attempt to write this down at Solstice Productions tutorials.
I also found a good tip for mp4 conversion (freeware): mp4cam2avi.