Installing Firefox on Windows
From MozillaZine Knowledge Base
This article provides a visual guide to installing Firefox on Windows, including Standard and Custom setup options. For general instructions that apply to all operating systems and for solutions to some common Windows installation problems, read Installing Firefox.
Downloading the installer
Make sure your computer meets the system requirements, then go to www.mozilla.org/ for the "stub" installer or go to this page to download the full installer for Windows in your language. Note: The installation instructions given below are based on the full installer. 
The file that you download will be named for the Firefox version number, for example, for Firefox 24.0, "Firefox Setup 24.0.exe" is the full installer and Firefox Setup Stub 24.0.exe is the "stub" installer. You can save the setup file to the desktop or any other location on your hard drive. When the download is finished, close the browser and any other running programs.
Starting the installation
In the Setup Type dialog, the "Standard" option is selected by default.
Click the Next button to install Firefox with the recommended options. The Completing the Mozilla Firefox Setup Wizard dialog will then appear. Click the Finish button. If you leave the "Launch Mozilla Firefox now" box checked, Firefox will then start (see below).
Select "Custom" in the Setup Type dialog (shown above) if you want to choose where to install Firefox and what shortcuts to create. In Firefox 2 and below, you will also have the choice to select some optional components.
Choose Optional Components - Firefox 2
You have the choice to select the DOM Inspector, which is not installed when you choose the Standard setup. You can also choose whether or not to install the Quality Feedback Agent, which is installed by default in the Standard setup.
Note: The DOM Inspector is available for Firefox 3 users as an extension. In place of the Quality Feedback Agent, Firefox 3 includes the Mozilla Crash Reporter/Breakpad as a core component and provides no option for removal.
Choose Install Location
This option allows you to choose the "Destination Folder", where Firefox is installed.
Set Up Shortcuts
You can choose create a Firefox shortcut icon on the Desktop, Firefox shortcut icons (for both a normal and a Safe Mode startup) in the Windows Start Menu Programs folder, and a Firefox shortcut in the Windows Quick Launch bar. These shortcuts are created by default in the Standard setup. Click the Next button to create these shortcuts.
Warning: If you choose not to create Firefox shortcut icons in the Windows Start Menu Programs folder, then the Mozilla Firefox (Safe Mode) shortcut will not be created. See the Safe Mode article for more information.
Choose Start Menu Folder
In Firefox 2, click the Install button, as shown above, to complete the installation.
Summary - Firefox 3
Completing the installation
Click the Finish button.
Note: When Firefox opens, you may receive a prompt asking if you would like to set Firefox as your default browser, if another browser is currently the default. "Default browser" means the browser that opens when you click a link in your mail application or when you open an Internet shortcut or HTML document.