I have a Mac Mini connected to an external HD. Sometimes while I'm not using either, the HD will just come on. The Mac itself usually isn't doing much when this happens. Most of the time it's just resting on a menu in XBMC. Does anyone know what the OS could be doing to prompt this? The spinning never lasts more than five minutes, which is when the HD is designed to sleep so that implies to me that it's just accessing it briefly rather than doing anything for an extended period.