mid-2010 17" mbp Getting a crazy rotational vibration, intermittently from the left side of my open mbp. I can't tell if the HDD is going bad, or if the FAN is going bad. I want to confirm one or the other so I can order parts and fix it. Vibration occurs sometimes at startup (at cold temp, no memory intensive apps yet) AND after long hours of use (at hot temp, with plenty of intensive apps running). It lasts roughly a minute, then is gone. I have SMCfanControl installed, and I check fan rotations when the vibrations start, and Left vs. Right are maintaining equal speeds. I can also check the HDD with Disk Utilities and get no issues. How do I figure out the guilty part?