Strange sound

I think my videocard is making a strange sound and it isn't the cooler. I'm having some issues with my cooler on my card but i think that isn't the source of the sound as i unplugged the cooler of the videocard and yet the sound didn't stop. Finaly, i have a Daytona FX5500 256MB/128bit (with no overclocking). When i unplug the video card from her AGP slot and start the system, that sound stops, when i replug it in, and start it again the sound is present. Even when i stop the cooler, the sound is there again. I have a GA-7N400-L Gigabyte mobo and an original Allied 400W power supply. I think the source of the sound is the videocard itself (not the cooler or anything). I consider to be of use that you know this sound is similar to what i've encountered few months ago, when i simply moved my mouse when runing a 3D app, but this time it's much louder (annoying).
I would surely be thanking you if you could just point me the faulty component.

i have a spare power supply. that one came with the case and was just only 350W (it isn't certified) so i replaced it with this allied which is great (certified at 400W + its silent and i didn't have any power issues as i have 1xdvdrw + 1xcdrw + 1xhdd).
I doubt it is the power supply that's making this strange sound but i will replace it and let you know what happend.

it's like the sound that comes out of an old hard-drive but it's a sound of high frequency (like a dog whistle). i've checked it with my old power supply but that one makes a much louder noise i couldn't hear this stupid noise. And it accentuates when the hdd works intense (at least i guess so). Could it be from the power consumption ? As i said, when i disconnected the video card and started the system it stopped.

PS: Now i have disconnected both optics (dvd & cd) and still it doesn't stop. After that i disconnected even the hdd and it didn't stop. So the power consumption ideea is out (OMG, anyway it's 400W certified and it's a rig with a Sempron 2600+ skt A; low-end system anyway).
I have only 3 coolers in the system: one i have no doubt about its within the power supply; second one is on the cpu, neither does this make any sound; third one is on the video card, which i stop and no change occurs.
So this leaves me to one single suspect: video card circuits ?? i have no clue if it can be possible or not.
Please help once again.

it's too obvious that the faulty component is the videocard itself but i didn't knew that some integrated circuits can make this sound. i will try and see what happens if i plug another card in the agp slot. anyway i'll probably get myself a new video card.