XPS m1330 both head phone ports simultaneously

I installed windows 7 on my xps 1330 recently. Since then I have not been able to use both head phone ports at the same time. Each one works by the m selves but if I plugg in to both, only the right one works. One would think that it would be as easy as sellecting simultaneous use in some property setting... but no.

I have the standard sound driver that came with the computer. I have tried to find a sollution online without success (obviously).
My service warranty at dell has run out so I cannot send them an email and ask. 

Has anyone had similar problems and found a sollution?
Does anyone have a sollution without having had the problem? 

Anny tips are welcome.