I first noticed it a few days ago when I walked in the room and the Computer was off. I'm not in this room often when it's off so I'm not sure how long it's been going on, It could have ben going on unnoticed fir a very long time, but im not sure. But the noise is comparable to when your ears are ringing. Now that I've noticed it it's driving me nuts, I'm pretty sure it's making the noise when the pc in on also, but it's muffled by fans and such. If I turn the computer off it's very noticeable since it's the only noise in the room, and if i switch off my power supply the noise steps down in pich until it's gone. It's very strange. I've read it may be capacitors or a bad Power supply, but I just got this new 500w Antec Power Supply this thanksgiving, so it sucks if it's going bad. Any Ideas?
see if the noise is coming from psu as when off some psu's still use power. if have optical mouse, is the laser still on when windows shut down?