I just replaced the original 640GB hard drive from my Early 2009 24" iMac. I installed a Seagate 1TB 7200 RPM drive. The install went well with only a broken microphone cable connector - whoops. The newer hard drive runs wonderfully however, I now have what I would refer to a harmonic vibration/resonance that I presume is coming from the hard drive. The vibration/resonance is consistently pulsing from nearly silent to quite loud. Has anybody else experienced this and what did you do to resolve the problem? Normally I would not worry about it but it seems to be the perfect vibration/resonance to gives me a headache . Thank you in advance!