Chirping PC... GPU? CPU? Shrew infestation?

PC is a Medion Titanium 8000, originally consisted of:

• 
  Medion-branded MSI mobo (don't remember #)
  Pentium 4 2.66GHz CPU
  Integrated Avance AC'97 audio (5.1)
  GeForce Ti-4200 + video capture, 128MB 8x AGP
  256 DDR RAM
  SATA HDD
  CD+-RW
  DVD-ROM
  Unknown power supply

RAM was soon upped to 1024+256, years passed with no problems.

Power supply fan failed while I wasn't around, overheated and died, took out graphics/capture card as well. I replaced PSU with a 350w and GPU with XFX GeForce 6200, 256MB DDR2 8x AGP. I didn't change or bump anything else.

For a few weeks, it make an ultra high-pitched chirping at times when graphics were changing, scrolling webpages, etc. This was usually more prevalent after a cold boot when computer had been off and cold for several hours. It's so high-pitched that some people can't hear it, but it's horrible to me.

I'm currently running from a Knoppix disc because the hard drive was intermittent and is out for warranty replacement. I guess the sqeaking had stopped for a few months, because I've noticed that it started again. It seems to be related to graphic changes, mostly when I scroll, minimize/maximize windows, and when webpages first load (sometimes before they are actually displayed). I suppose it could be CPU load, or GPU when performing ops or caching to VRAM. There also seems to be a slight inconsistency to it, the way a busy hard drive makes imperfectly-timed clicking.

It's not that loud but it's so high-pitched, it's like having a needle piercing my eardrums! Even wearing earplugs doesn't seem to muffle the angry shrews inside the computer. Maybe the hamsters need their wheels oiled? rolleyes

Does anybody know what this is or what to do about it? Thanks.

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In other news, this forum isn't correctly supporting the transparency of my avatar pic...

 

Do you have a CRT monitor? I had that happen to me before the monitor gave up the stinking blue smoke of death.

 

It's a CRT monitor, but the sound is most definitely coming from the PC tower somewhere.

 

Switching power supplies, squeal when they're loaded down. You seem to have good hearing because, as a rule the squeal can't be heard by most people. However, the most likely culprit is dirt in the bearings of one of your fans. I test them with a pencil - the sort with an eraser on the end. I press the eraser end of the pencil against the centre of the hub of the fan. You don't need much pressure. If the squeal changes pitch, then I've found the bad fan. Don't forget the fan on your video card.
.

 

No, sorry... it's not a fan or any other type of bearing. I checked all of the fans after the old power supply's had failed. The GPU on the graphics card has passive cooling anyway.

The sound seems to only occur as graphics change, the onset it immediate, and it stops just as suddenly when the graphics stop loading or changing. As one can imagine, with a semi-modern computer this all takes place in less than a second. Definitely not a bearing.

It doesn't do it all the time either. It went away for months, now it's back, but it doesn't always make noise either.

Now that it has quieted down some, it sounds sort of like the ultrahigh pitched chirp that an optical drive can make while reading. An open PS2 comes to mind. (I had to get a fliptop after a cat broke the 1mm guide pin on the standard tray). But still, it can't be an optical drive because it happens even with them unplugged... that's just an idea of what it sounds like.

 

Since you have great hearing, use a paper towel tube to find the culprit, always worked for me.