Faint high pitched spinning noise that isn't a fan

[peacetilence]

I'm trying to make my case as quiet as possible but for some reason I still get a high pitched noise that sounds like a fan spinning. I'm proof positive it's not a fan though becauseI removed them all (including chipset fan) and still got the noise. It thought it might be my PSU so I removed it's fan as well and still had the noise. It's not from the GPU's, I've tested it without them in the PC.

It's weird because it sounds like it's coming from the hard drives to me. I've tried to pinpoint the problem probably 100 times today because it's driving me nuts and still couldn't figure out if it was the hard drives making this noise. I installed the hard drives using rubber gromits, had the noise, I now have them individually lying on top of pieces of felt and I still have the noise. I want my pc to be dead quiet and I've done it with fans except for the high pitched noise. Does anyone know if it's possible hard drives could make high pitched noises like this? It sounds almost exactly how a fan would sound if it were reverberating in the case except it's much quieter, high pitched and sounds like it's coming from the hard drives.

I've removed them from the case and everything to try and test it out but I'm stuck here trying to figure out what this is.

 

[MrkXCeL]

PSU/RAM/GPU can make a noise like this.

I've got a Shuttle system, and when you put a heavy load on RAM or VIDEO card ram, u can hear the chips screaming (though very quietly) but it's there, and if the Shuttle is running cool at the moment, the whine is louder than the fans.

Run the harddrive externally somehow, listen to it then, all drives have some sort of motor noise when idling, even laptop drives.