I had a stock 7,200 hitachi drive but it was only 320gb so upgraded to a a WD Scorpio Black which has the capacity and the speed but seems a bit noisier to me which I really don't like - I'm sure my MBP fan comes on more too at high speeds. Strangely when i press the macbook case down to the right of the trackpad (above where the hard drive is positioned) it sounds much much quieter and then when I remove pressure from it it reverts. Does this indicated viberation? I'm looking for a 750Gb 7,200 drive for cloning purposes so may switch out the the scorpio black when i get the new one. The two i'm looking at are: Seagate Momentus XT - I like the SSD type performance boosts Hitachi Travelstar 7K750 Which is quietest? Is there much difference are all HDDs quite loud really? This scorpio black seems more noticeable than any i've had before. I don't really want to spend £300 on a 500gb SSD especially as if I need to upgrade my late 2008 mac anytime soon the new mac will have built in SSD anyway. I am a little bit tempted though!