When I first got my MacBook Pro, it was dead silent running. Now, there is always a small "whirring" sound coming from the left under the speaker. Almost like a fan, but I've heard this is the hard drive... I also heard that its only the Hitachi one that does this... (I have Hitachi HTS542525K9SA00, according to system profiler) If I take it to an apple repair centre would they replace it for a quieter one? Or could I replace it myself without Voiding the warrenty? (And if so, which one would I replace it with?) I'd really like this laptop to be quiet.