sarah cunningham's dashboard

dell xps m1330 plugged in not charging. My laptop will not turn on unless I have the ac adapter plugged in and if I remove it when Its turned on it switches off completely. It won't charge at all the battery live remains at 0% it says it doen't recognise the ac adapter even though its the only one I'v had. I read other peoples similar problems and they said it was to do with the motherboard. I only got my motherboard replaced 3 months ago due to a graphic card. Pleas help I in the middle of doing a thesis and could do without this problem