I can't get any sound on my PC. I've tried a couple of different speakers that work on other computers, but no luck on this one. I'm wondering how I can determine where the error is? We can plug headphones into the headphone jack on the front of the PC and can hear sound that way. But plugging speakers into the back jack doesn't work. SInce the headphone jack generates sound, is it likely that I could get some speakers that connect via the USB port that would work?