How to Change the Icon to Your Chosen Icon in the Firefox Window and the Bookmarks Dialogue Window.
You can change Firefox's default window icon to any icon you want, for example to internet explorer, by following these steps:
1. Go to the folder you installed Firefox in (It's usually this one: C:\Program Files\Mozilla Firefox\) and then go to the subfolder chrome.
2. While in chrome, create a new subfolder called icons, then go to that folder and create yet another subfolder called "default" The full path to this folder could be C:\Program Files\Mozilla Firefox\chrome\icons\default\.
3. Choose the icon you want to use (on Windows use .ico files) and then place it in this folder and rename it to main-window.[.ico], e.g. "main-window.ico" for Windows
After this is done, restart Firefox and you should be able to see your chosen icon in the title of the browser windows, and in the taskbar. I would suggest IconPackager to change the shortcut icons on the desktop or PC menu.
Have fun, and post comments below for support.
Make Firefox themed EXACTLY like Internet Explorer for Vista: [link]