I have a Dell Studio 1555 running 64-bit Windows 7. I also have some harmon/kardon external speakers I want to use. When I plug in the harmon/kardon speakers it makes sound play exclusively through those. I want the sound to play through both my laptop speakers, and my harmon/kardon speakers at the same time to create a kind of surround sound. How would I do this? Thanks in advance for any help.