ok i have noticed this since i installed panther on my 1.25gig PB. open finder in colunm view and highlight (not open) a sound file / video file / toast audio image file etc. make sure that the "preview" tab is in its on postion. now i have to be in a very quiet room to hear this but every time i do the above i hear a high pitched noise come from the PB. as soon as i deselect the file and move to highlight a no audio / video file etc, the sound stops. if i go back to highlight an audio file the sound starts again and remains untill the audio / video file is deselected. note this sound still comes from the PB even with the speakers muted. the sound does not occur when using apps like itunes etc or over the speakers when playing audio or video. the sound is only present when a such a file is highlighted in the finder / in colunm view / with preview on. please try this and see if yours does the same, this as only been the case since i install panther, and i stress you have to be in a quiet room to hear this. andy.