Mic with headset USB attached to Windows 7 ruing on Dell optiplex 780 not working

3.5mm headphone and mic jack work fine. I changed to a USB-coected headset and the sound was faint. Switched back to a 3.5mm solution. Sound was acceptable but the people I talked to said the sound was faint.

Just installed a Siberia, Raw Prism, gaming headset. The mic works fine, but sound plays through the inteal PC speaker. I've been to Dell, Microsoft and your support. All indicators show the headset as installed. The mute button delivers a single tone and the headphones are lighted up in orange.