Apple replaced my MBP (core duo) motherboard a year ago for this problem and that fixed it in '06. BUT, I took my Mac in to replace a fan and they switched the MB too. Now, the problem is back! Assuming they didn't put an older MB in, there's still a problem in '07. I wonder if it is present in a certain percentage of MB's and in my first repair they were careful and checked the noise since it was my complaint that time. I'll give the Apple part #'s in case people are interested.
630-7705 previous, no whine
661-4044 current logic board whines

Has anyone successfully intervened physically with either sound dampening or putting epoxy on some capacitor(s)?