I have just replaced my old HP Pavilion tower with a Dell Optiplex 3010. I want to use my old 5-speaker system as before, which has 2 small jack plugs (a green and a black), but there is only one speaker port at the back of this PC (green), which only powers two of the speakers, plus the woofer. There are other ports marked for a microphone and something else, in which I have tried the second jack, but to no avail. Is there an easy solution? (The speaker system is an old one from Cambridge Soundworks). Thanks!