Re: Overheating and buzzing
What brand power supply do you have and the watts on it? Maybe your power supply is about to die and is making the buzziing sound.
Take out your new video card and use the integrated one, does it still make the noise?
Is the new video card installed properly with the integrated graphics disabled?
Was the old video drivers uninstalled so conflict don't occur.
If you still can't find out where the buzzing is coming from, disconnect everything except for the bare minimum to narrow it down.