Bug 228163: en-US Windows localization uses "Help" and not "?", unlike the french and german one. It's up to the localizer to decide what to do, but now, it can tweak the windows build without affecting other platforms.

browser/base/locale/browser.dtd

@@ -167,8 +167,10 @@
 
 <!ENTITY helpMenu.label         "Help"> 
 <!ENTITY helpMenu.accesskey     "H"> 
-<!ENTITY helpMenuWin.label      "?"> 
-<!ENTITY helpMenuWin.accesskey  "?"> 
+<!-- LOCALIZATION NOTE some localizations of Windows (ex:french, german) use "?"
+                       for the help button in the menubar but Gnome does not.   -->
+<!ENTITY helpMenuWin.label      "Help"> 
+<!ENTITY helpMenuWin.accesskey  "H"> 
 
 <!ENTITY releaseCmd.label       "Release Notes">
 <!ENTITY releaseCmd.accesskey       "R">