Thanks for the response.
I was reading some posts yesterday and found out I might be out of luck.
I’m using Vegas Movie Studio Platinum 9.0. I render my video as mpeg-2 with a separate render for .ac3 audio. (Both files have the same name). According to other posts, when I drag the mpeg-2 file into DVD-A the audio file should follow it automatically.
This didn’t work for me. I suspect it is because my version doesn’t support .ac3 audio because I only have the Movie Studio version. (At least that’s what I read in another thread).
My work around was to burn the DVD from a .wvm render. Quality isn’t what I hoped, but it has sound and does work in winDVD. (I’ll have to look for that WMP plug-in).