Hi, I've stumbled upon your post, as I've recently had issues with high pitch sounds as well.
Tell me, is it JUST your system you're hearing these sounds from? or have you noticed other things making more high pitch noise than before?
I had a sudden on-set of super-hearing it seems. There are many variables, and I'm trying to figure out why, but I now seem to be able to hear high pitch sounds everywhere. My TV I've been using for years now drives me nuts! My new computer [E8400, Nine Hundred case, 700W Tagan PSU, 2xX1950 Radeon (old external crossfire), P5K-E Wi-Fi AP mobo, vx2240w monitor, 2x250GB SATA Barricuda HDD] makes high pitch noise too (not as noticable as the TV, but definately there). And to make matters worse, my workplace is PACKED with computers, servers, and anything else electronic.
Until about 2.5 weeks ago, I could maybe hear a an old CRT TV when it turned on, but usually wouldn't notice it after a few seconds or a minute. Now, the sound drills into my brain. When I finish watching some TV with the g/f, and try to go to bed, I can hear the high pitch ringing in my ears. (comparable to being at a concert and hearing the ringing, but much higher pitch).
A few things that I've read about which may be factors: I was sick with a sinus infection -- possible damage or cloggage of some sort. I went on strong antibiotics (Biaxin I think it was called), and accidently took a double-dose for my first one (I started hearing the noise just as I finished my perscription I think). Pharmacist said shouldn't be an issue, I might just taste MORE of the regular bile taste that stuff has as a side-effect. Often when I get sick, I get braunchitus (sp?) -- which I believe is chronic as I get it often (I've read that there was a study on people with braunchial asthma whom can hear in the 16, 18 and 20khz range). As well, I pretty much just built my computer, and right around this time I just got my two SATA HDD's, first ones I've ever owned, and due to the case it's very open for sound to escape. Oh, and I'm unfortunately someone whom cracks their joints quite often, including the neck, which I have heard can cause Tinnitus.
So for me, it's going to be tough to narrow down why I can hear these high pitch noises so suddenly... But maybe you can identify with one or more of these variables.
If it was ONE thing that I could hear, ok, it's deffective. But because I can hear the noise varying in volume as I walk around my house and/or office, I think I've just developed a keen ear for electronics -- which kindda sucks as I'm a computer engineering student planning on becoming a hardware developer.
I hope this helps!