it seems to be the outline of the vista explorer, i previously had vista installed, i deleted it then installed XP and the outline stays there all the time.
funnyly enough when i print screen it doesnt show up on the print screen :S
I'm assuming that you have a CRT. If that's the case then it could be a phosphorous burn in effect. I bet it will fade a little bit, but it's probably time to get a new monitor
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