These past few months I will be sitting working at my desk or on the computer, and i will start to hear like a movie ad playing over my speakers.  No internet explorer windows will be open, just AIM if that.  It starts to play and then is over in about 30 seconds.  I do not have Kazaa or anything like that on my computer.  I do not know where the source could be and would really appreciate it if anyone could help me. It is similiar to when browsing a website and those ads pop up and the girl will start talking or whatever,but in my case no windows are open.

Thanks