I am running windows xp on my pc and recently I have had a "blue box" with a lock inside that appears locked sometimes and then flashes to unlock. It is always in the center of the screen and briefly disappears at times. Whatever is on the screen this blue box with lock is always on top. This box appears the moment I boot up and I cant seem to get rid of it!!!!! Any suggestions on what the problem is and what I might do to eliminate this annoying blue box with lock????