Not quite. If your mobo has an spdif out (optical or coaxial), it can and will output DD or DTS from it. Because the digital signal is not being encoded by the PC, it's already encoded on the disc you're playing. Therefore all your mobo is doing is sending the (pre-encoded) signal down the spdif. All you need is software like PowerDVD that can output using spdif.
VLC, SMPlayer, FFDshow and others will all output DD or DTS through spdif but need more fiddling with to do it than PowerDVD.
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I was mostly referring to non-DVD sources. You can play pretty much anything over a digital connection (2 channel, 2.1, 3, 4, 4.1, 5, 5.1, 6, 6.1, 7, 7.1, etc)- that's not the issue. The issue is Sowk wants to playback everything in Dolby Digital 5.1. You can do this if your sound card supports Dolby Digital Live encoding, if it does not, then the only time you'll get the Dolb Digital surround sound is when playing a DVD pre-encoded with it. Your games and music would never play back in Dolby Digital 5.1 surround. Hope that makes sense.