Win 7 wont recognize headphones

We have a brand new hp machine. weve had 5 of the exact same make in the pastcouple of months with no issue.

But This machine wont play through headphones. if you play music it will only play through speakers Not headphones.

in control panel and sound it doesnt even show headphone.

how do i fix

I have the same problem

If the computer is new take it back. Headphones should work automatically, at least mini plug. If it's a USB then there may be something else...