DriverGenius U2AUDIO7-1 The Headphone Jack Does Not Work

I hooked it up and all works but the headphone jack. Her onboard sound on the computer does not work so that is why I bought this. I have tried other USB ports on her PC but still the headphone jack doesn't work. I have to unplug  her desk speakers just so her headphones can be plugged into that front audio port. How can we fix this problem. Please let me know.