there's a constant humming/buzzing coming from it. The harddisk is also making the occasional noise, but that's to be expected. The humming could be the fans, just how quiet is the imac supposed to be? (can you hear it running at all?) I don't want to nit pick, but if the humming is not supposed to be there I want to return it as soon as possible. I doesn't seem related to the brightness setting by the way. thanks in advance.