Application box will not go away

Hello, I run a triple Monitor display (multiple windows, not extended mode) on my desktop so I can run numerous programs at same time. On a small 22" Samsung monitor I used to run winamp to play music while I worked on spreadsheets on other two monitors. I notice ed that when I was not running winamp that a shadow of a dialogue box always stays on screen when the wall paper is displayed. When I run a program there it is not present. I un-installed winamp and it is still there on the wall paper. I re-installed video drivers..still there. I recently installed a new AMD 7970 video card and drivers.. still there. It does not really affect any running programs and is only there as this dark shadow box on my wallpaper on that monitor. Very weird and I am trying to figure out what is causing it and how to make it go away. It is not a burned image. It seems to be a ghost of the dialogue box that was part of Winamp. Not present on my other monitors wallpaper. Again, it is only seen when the wall paper is showing on that monitor. Anybody ever seen this and have any idea what can make it go away...I am becoming obesessed on what is causing it as I consider myself to be fairly computer literate (build my onw machines etc).