Copied from my PowerDVD User's Guide and "about" pages.
Audio
Supports 8-channel sound cards and output on up to 8 discrete audio channels. (*)
Certified Dolby Virtual Speaker technology allows you to experience virtual surround sound through 2 speakers. (*)
CLMEI (CyberLink Multi-channel Environment Impression) technology converts stereo sound to a multiple-channel output. Music and Movie modes are provided for your preference. (*)
TruSurroundXT(tm) Headphone, based on SRS TruSurroundXT technology, provides an optimized headphone environment. It features TruSurround, Dialog Clarity Enhancement, and TruBass technologies that bring virtual surround and virtual bass experiences to your headphones. (*)
Time Stretch, a pitch handling technology, permits audio playback from 0.5x to 2x speed without pitch distortion.
24/96 LPCM Direct Output supports 24bit/96kHz LPCM audio output with crisper, clearer sound. To enable this feature, you should have a sound card that supports 24bit/96kHz audio output.
Note (*): Full multi-channel DTS/Dolby Digital, Dolby Virtual Speaker, CLMEI and TruSurroundXT Headphone features are optional and may not be available in your version of PowerDVD.
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Also, look at this comparison chart I found that compares the different versions of five and six.
http://www.softwarecasa.com/pprod/212202compare.htm