How to hide systray icon permanently? (Even clicking the show arrow button)

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I have a download manager, and want to prevent caught from my cousin. but I know that you are thinking to right click the taskbar and click properties-customize and so on2x. what I want is to permanently hide the icon from systray bar even if he click the show hide icons button from systray. is there any way? or a software? rush pls! ^_^ thnx by the way