My box is only a couple of months old and I love it, but...from the outset whilst the box is recording I get quite a loud disk i/0 noise. Not a constant whir/hum but the sound of the data being written to disk. Every second you might register three or four 'writes'. They're not overwhelmingly loud and when the TVs on you can barely here it but in a quiet room it's audible. It's noticeably louder when recording HD. Just wondering if this is normal or if other boxes are completely silent?