Has anyone else seen and resolved a similar issue to this? On my G5 2.5GHz Dual with X800XT when idle iStat Pro reports fans speeds: CPU B Exhaust 300rpm CPU B Pump 1250rpm CPU A Intake 300rpm CPU A Exhaust 300rpm CPU B Intake 300rpm CPU A Pump 1250 rpm Drive Bay 1000rpm Slots 122rpm Backside 51rpm Despite this after about 5 minutes of use either after waking from sleep or a restart there is a fan that get louder and it is a really grating pitch that gives me headaches if I don't put on some music a DVD or something to drown it out. If I put the Mac to sleep it goes away again but only for a few minutes. If I give the machine heavy tasks like video encoding the cpu fans etc speed up as expected and with a demanding game I can hear the video card fan but this constant noise is different to both these situations. I have tried shutting down and up plugging the mains, messing with energy saver processor settings and before I had a problem with my upper drive bay (now getting IOATA controller blocking bus errors if I attach any drive in this bay) the problem still happened when booted from either hard disk, one with 10.4.11 and the other with 10.5.2. I have also blasted the dust out of the case with compressed air and the problem persists.