In all cases I've found that to be some addon from the machine's maker. That is from Dell or other maker. Given no machine details no one can guess what it was or where to find it.
before i reinstalled windows vista whenever i changed the volume by holding the "fn" button and then volume up/down, there was always a small blue box on the top left part of my screen showing the volume level. Now after i reinstalled vista when i press the buttons it does control the volume but doesnt show any box with the volume level like it did before. Any Ideas?