Ok, ever since I got it, my ASUS A7N8X I've had a small ammount of noise coming through the audio out jack. When playing music, this noise goes away (obviously). When the computer is idle, (like browsing the internet) there is usual whine in the speakers. I've checked thoroughly and found that the motherboard is the source of the noise, and not interference from power cables and the speakers.
Now heres the killer part, I just recently noticed (3 days ago) that when you have a USB thumb drive plugged in, the noise dissapears. So for now I've been keeping my little 256MB Sandisk Cruzer plugged in to keep the noise away.
Also if you have a thumb drive and are getting noise through your speakers, test out this temporary fix to see if its repeatable on other systems.