Just got this 27' iMac after a long excited wait for her, and 24hours into ownership a deep hum has appeared, I like my quiet computers, so I would have noticed this beforehand. Installed SMCfan control but all fans speeds appear on low!!! . ODD 1150RPM . HDD 1100RPM . CPU 940RPM Done a full SMC reset, with no success, really gutted as I expected more from this machine. Is this the dreaded HD noise I recall reading about?