Old computer speakers won't work with new com

Hello, I just bought a new computer tower. I unplugged everything from the old one and into the new. When I tried to play music on the new computer, there was no sound in the Boston Accoustic speakers from my old computer. They worked yesterday. I tried the speaker jack in the back and the headphone jack on the front of the tower. Should the speakers work? Is there anything I can do to fix it, or is it possibly the computer? Sound does come through when I plug in headphones.