Welcome to DHC!
In PowerDVD click on Configuration (the toolset), then on the Audio tab. Here you will see a pulldown menu for Speaker Environment. Set this to two speaker. For Output mode, you have several options you can play with; Stereo, Dolby Virtual Speaker, or CyberLink Virtual Speaker.
By clicking on the Advanced button you will see additional configuration for Dolby Virtual Speaker and CyberLink Virtual Speaker. There is also a Misc tab where you can enable or disable LFE (Low Frequency Effect).
Hope this helps!