Bad inductors?
Inductors vibrate during system operation due to magnetostriction, producing audible noise. On a motherboard, inductors typically look like donuts with wire wrapped around them, or small coils of wire encased in a plastic square. While there is usually glue on the inductors to suppress this vibration, poorly applied, damaged, or otherwise failing glue on one or more inductors can cause this noise.
Applying glue from a glue gun may help solve this problem.
Note that you may want to pinpoint the source of the noise before attempting to repair it. Capacitors are often (incorrectly) blamed for this behavior.