INternal speakers not working on my notepad

Hello,

I have a new samsung x320 notepad, internal speakers used to work now they arent, however external speakers work if I hook them into headphone plug?? could anyone suggest why the internal speakers arent working, on skype it says my speakers are fine, but i cant hear others speaking , they can hear me. I cant play videos etc no sound unless I plug the external speakers in?? I have windows 7