High frequency sound from computer

I am hearing a high frequency sound coming from my new computer. I am thinking that most likely it's the power supply, but I cannot pinpoint the location. It's not something that you hear in one hear and not the other, it sounds like it's originating in the middle of my brain. It's such a high frequency that I doubt everyone could hear it, although I'm sure it would drive a dog crazy. Kind of like the sound my 6 year old CRT television makes, but not nearly as loud. I'm not entirely sure that there's necessarily a problem, maybe it's just a noise that my components make. Anyway, I'm wondering if anyone has any ideas as to what the problem may be, how to better pinpoint the source, and whether or not something is wrong. Here are my specs:

EVGA 680i
Silverstone Zeus 850W
QX6700
EVGA nVidia 8800 GTX x 2 (SLI)
Coolermaster RC-830 (1 fan front, 1 fan back)
X-Fi Plantinum
Western Digital Raptor 150 GB x 3
Plextor PX-755SA

I tried unplugging all of the fans, one at a time, and the noise never went away. My guess is that it's the power supply. I've heard similar complaints about other power supplies, but I haven't heard of any complaints about the Silverstone 850W. My real concern is that it's something other than the power supply, like the motherboard. If it's not the power supply, it could be a very time consuming project trying to identify and fix the problem.

I don't know if this helps with your problem, but a few years back my dad's computer was making an awful high-pitched noise, and it turned out to be the hard drive. It was working just fine, but the noise was terrible.