Dell XPS M170 Power Issue, Please Help!!!!!

Hey guys, I have a xps M170 that has been working fine for a while. But last night When I went to turn my computer on my batterie light was flashing yellow and there was a high ptich humming sound from the computer.

When the ac adapter is pluged in I get this Humming sound, as well as the Batterie will not charge. The computer is not reconizing the ac adapter.

Now when the computer is off and I plug the ac adapter in i get a flashing green Batterie Light.

Any ideas? I think my ac adapter my be bad but I dont want to spend the money if its somthing else.

Thank you Paul