Weird Buzzing from around CPU during HD activity

[Sendorm]

Hello, my first post.

I've a working FTP server on a 100Mbit/s LAN and its quite busy, working at around 40Mit/s all the time.

There is a buzzing coming around the cpu area fully correlated with harddisk activity while sending files over the FTP, whenever the HD activity led is on, there is the buzzing. It does'nt make noise during normal harddisk activity, loading, windows apps etc.
I am %100 sure, it has nothing to do with harddisk drive because I've changed the old drive recently.

My main board is asus p4p800se.
I've succesfully silenced my rig so every little buzz is appearant at the moment. I've tried pinpointing the source with no luck. And I am almost certain that the noise is not coming from the psu (which is a tagan 330w).

I've touched nearly every component at the evident source of noise, but felt no vibrations what so ever.

Any one had similar experiences with hd activity correlated buzz issue? And of course any idea how to solve this.
Any help is appreciated.