Mozilla Firefox®, Portable Edition is the popular Mozilla Firefox web browser bundled with a PortableApps.com Launcher as a portable app, so you can take your bookmarks, extensions and saved passwords with you. We saw how to set Firefox Portable as the default Web browser in Windows XP. Here is a tool which can register Mozilla Firefox Portable Edition with the Default Programs tool in Windows 7/Vista.
Register Firefox Portable with Default Programs
1. Download registerfp.zip and save to Desktop.
2. Unzip the archive and extract the contents to a folder.
3. Double-click the file RegisterFirefoxPortable.exe to run it
4. When you see the User Account Control dialog, click Allow
5. Click the Browse button and locate the Firefox Portable executable
6. Click Register
Editor’s note: If the drive letter for your removable device (which contains Firefox Portable) changes, you’ll need to re-register the program using this utility.