I recently upgraded to a new LCD 24" wide screen. I had to put in a video card to support it, actually one that I salvaged out of my parts pile, originally bought for my son's game machine. Something odd happens now: When I scroll in certain applications, the computer makes a corresponding noise. Its kind of a faint, high pitched buzz, almost a ring, that comes from the box. It mostly happens in AutoCad when I drag large text blocks but in other apps less pronounced.

Any ideas what it is?