As far as I know, PowerDVD is the only program that can pass through AC-3 audio. Unfortunately, I don't have an AC-3 capable sound card, so I don't know for sure. I'm emailing one of my friends to see if he has gotten it to work, and as soon as I get a reply, I'll let you know.
BTW, LUCIDGUY. Great insight, SINCE THAT WASN'T EVEN WHAT Noriaki WAS ASKING. Go away you little freaking troll.