SRS audio sandbox/audio devices issue

Hey guys,
I have the srs audio sandbox for pc windows 7 installed. When I click on the speaker icon in the bottom right corner, it shows two devices: High Definition Audio Device and SRS Audio Sandbox (WDM). When I drag the volume slider for the HD Audio Device, I get the ding sound. However, this doesn't happen when I move the volume slider for the SRS Audio Sandbox. I have the SRS speaker set as my default device, but when I play movies on WMP, vlc, quicktime, there is no audio. However, videos played on firefox or chrome, as well as music in itunes, produces sound (through the HD Audio Device, and not SRS, though). Can anyone tell me what to do? Let me know what other info I should provide. Thanks!