looks like you're right. I ripped the DVD no problem, but when I looked for the AC3 files, they were nowhere to be found. All I could find were VOB files, so I assume you need both Nero AND the plugin before you even rip the DVD (I didn't when I ripped it, so now I'll try it again after buying the full-blown Nero + plugin)
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That's because the VOB container contains audio (PCM, AC3, ...) AND video. I use DVD Decrypter (http://www.afterdawn.com/software/video_software/dvd_rippers/dvd_decrypter.cfm) to rip and PgcDemux (which you can find here: http://jsoto.posunplugged.com/dvdtools.htm) to demux.