Thanks a lot, guys. The pop-your-card-into-the-oven trick seems quite interesting if it can revive the zombie that my nVidia XFX 7600GT is today. Will try it and let you know.
@ Mr. DBZ: I believe my power supply is causing the sound, though I couldn't be sure. It is definitely not the fan. The power supply is an iBall LPE223-400. Yes, it is while I'm using the onboard video, especially when I play a CD or a DVD. And this was happening even when my card was running fine.