Do you mean the Firefox menu bar -- File, Edit, View, History, Bookmarks, Tools, Help -- or a different part of Firefox's toolbar area? This article describes how to turn on the menu bar (it's optional on Windows): [[Restore the Menu bar in Firefox]]. The the menu bar still doesn't appear, is it possible the browser is sticking up past the top of the screen? That probably would hide the usual 3 Windows buttons, too, so you could check for those.