Audio playing in background?

I have Windows XP, recently i've noticed that audio that sounds like a newscast playing in the background of my computer even though i have nothing running. at the end of each newscast the person speaking says something about "marketnewsvideo.com." i don't know if that is relevant but i thought it might help. I just want to get rid of this annoying background noise, i can't watch video, play games, etc. because there is always sound overlapping. Please, i just want to know how to get rid of this.