Another win! Thanks for this ancient thread. My ProMedia 5.1 recently started buzzing loudly through the subwoofer, and I thought it was toast.
I first replaced the two easier capacitors on the power supply board that others have replaced. No dice.
Then I moved on to the two mentioned by stpete cooling. After carefully replacing them and plugging the unit in, sweet silence! (Well, sweet until I connect my speakers back up and run some music through it!)
Thanks!