Is this when playing all clips or just certain one(s)? I don't know if this has anything to do with your problem, but are you aware of the various "zoom" settings? I'm currently using Version 8 of WMP and under the "View" menu, if I hover the mouse cursor over "Zoom", I can select from "Fit to window", 50%, 100%, or 200%, with keyboard shortcuts of Alt-1, Alt-2, or Alt-3, respectively, as alternative means to select among the last three settings. And whatever setting I'm curently using seems to be saved between sessions. Is it possible you could have unknowingly hit Alt-1 or otherwise somehow set the zoom to 50% without realizing it?