After three years(I think) my computer is making a loud screeching soound

I disconnected every fan one at a time(even the CPU fan) and none of them stopped the sound. At first, I thought it was my power supply, but the sound gets louder as I get towards the main exhaust fan at the back of my Stacker 830. Can my CPU make such a sound? It's a loud screech that even my family downstairs can hear, yet I'm still typing on the computer right now without a problem... It just started all of a sudden while playing World of Warcraft. So, would anybody know what it is?

If a bearing goes, it can scream. Are the fans free of debris? The extra drag can cause a fan to be noisy, seen it a couple of time. Failing that, probably a bearing going out.

Yup, sounds like a bearing going bad. If you've ruled out all the fans, it must be the fan in the power supply. Had a cheap PSU years ago that was making that screeching noise, I just ignored it and eventually the fan must have failed and the PSU popped(literally).

If you are certain it is not a fan, try this. Remove VGA(s), Sound Card, all PCI related hardware. Now discharge the MB and re-install each component one at a time, see if the sound is still there.

I solved the problem a few minutes after making this thread, but the forums were giving me a database error, so I couldn't post.

So... I looked at the fan on my ATI video card and for some reason, they put a sticker on the inside of the fan opposite of the outside sticker and it seemed to have become unstuck with heat. It was pegged in the corner with dust or dirt which made the sound as the fan spun. I just had to dissemble the cooling unit and remove it.