Headphone help

Hey guys, i use skype on a regular basis, and my headphones won't change to my default device. So when i use skype, only that sound is played through my headphones, while the other sounds only play out of the speakers. i've tried disabling the speakers, but it just won't let me change the headphones to my default device. what do i do?

By the way, i use an hp Pavilion Entertainment PC (laptop), with 2 jacks for the headphones.