Whenever I play a Steam game or something like CoD 4, the hard disk (I presume, situated on the upper left of the Apple logo for someone looking at the screen) makes a whirring noise, IMMEDIATELY disappearing when I switch back to the Finder or any other program. It's definitely not a sound issue, as I've turned off the volume to test it...I thought about possible dust accumulation in the area, but it definitely seems like a HD issue...is it going bust or is it just making noise all of a sudden? I've tried opening folders, files etc. and can't replicate the noise when NOT playing a game (is it defragmenting in real time, therefore leading to the noise? No idea!)... Your help is highly appreciated.