Windows 7: Windows NOT automatically reducing sound when in VoIP

Hi there. I had originally disabled the feature that lowers all other sounds by 80% when in a voice call, however now that I figure I need it back on, since my VoIP program (Steam) isn't loud enough compared to other sounds, it just isn't lowering the other sounds. I tried with both the 80% and 50% reductions, and neither made a difference. I did install a new sound card recently (Asus Xonar DG), however the problem was still ongoing before I put it in. Any help would be appreciated.