It depends on your window and/or session manager. Under RHL you have a choice of number of them - so make clear which one you are using (Gnome, KDE, TWM, probably fluxbox, blackbox, Xfce).
All of them have a kind of panel and panel applet which holds icons/buttons for minimized applications. It's possible, if you remove the applet from the panel, to lose track of minimized windows. So, help system, FAQs and READMEs for appropriate window/session menager are you best friends (as usual).