Hello, you can also get some noise-reduction ferrite core, such as this :

http://www.shinemicro.com/images/ferritethumb.jpg

Perhaps you have some already clamped on some device's wire (digital
camera, AC/DC tranformer, modem, etc...).

If you can un-clamp one a clamp it on your laptop power wire OR audio
line wire, just check if it helps...

I did that on my AC/DC adapter of my SW radio, and it helps reducing (a
little) incomming RFI.

Charly