Acute sound coming from speakers and headphones

Hi,

So I recently bought a new computer. I had to remove the motherboard and reinstall it. I installed windows xp professional 32 bits. Here are some components of my computer:

Asus P6T motherboard
Realtek High Definition Audio

So, I installed the drivers and everything, and something weird is happening. Whenever my speakers or headphones are plugged, I hear this very low sound coming from it. If I lower the volume to 0, it stops. Another thing, when I disable the audio drivers, then I activate it, the sound stops for a couple of seconds, then starts back. I may have an idea of what is causing this. Just next to the audio plug in for the speakers, there is a fan wire along the plug. Could it be magnetic interference? But still, I get this problem with my headphones, which plug is on front and not back.

I reinstalled drivers and everything and it's still making this noise. What can I do?

Thank you

Edit: New fact. Yesterday when I turned my computer off, there was still the same noise, with a lower frequency, coming out of my speakers. I guess it's a material issue, but I'm not sure what it could be.