I Can't Turn Up The Volume

I am using these generic monitor mounted speakers with no volume control or built in amplifier. I have all the volume controls on my computer turned all the way up and nothing is muted. I am getting some sound, it is just very low. My speakers are plugged in right. I recently downloaded winamp and when I turned up the volume/amplifier control on winamp it seemed to help a little, which leads me to believe that there may be some program that I can download that will amplifiy the sound. Can anyone lead me in the right direction of where to find software that may work?

Thank you