Hmm - looks like Apple, in their wisdom, have used a wacky PSU design. Which costs Â£145 to replace with no assurance of less noise
This is bad news as it looks like that's the prime noise source as it has two 40mm fans in it which would tie up with the high pitched tinny sound it's making.
If there's anything I can do that doesn't cost a lot, the company would probably spring for it.
I've noticed a small fan that appears to draw air in from under the side panel and direct it over the optical drive. As this drive is never really used, I'm figuring this should really be redundant.
Even if it isn't, the machine shouldn't be under much stress as it'll be getting used more or less solely for email & web browsing so I've got to figure it can get by without the airflow from a partially obscured, low profile 60mm fan.