Whenever I use my microphone, there is a strange humming in the background. I'm certain it's not my PC because if I cover the the mic with by hand no ambient noises can be heard, and the humming gets really loud. I'm using my new Xonar DG, and I have no idea what's doing this.
Are you running the headset through the front panel audio ports? If so, the problem may lie in a ground loop. I had a ground loop problem with my Vulcan and a Xonar DX running through the front panel of an Antec 1200