There are two ways to install Firefox 4. You can either upgrade from Firefox 3.5/3.6 or you can do a fresh install.
Upgrade Method
When Firefox 4.0 was release, Mozilla also released updates to Firefox 3.5 (3.5.18) and 3.6 (3.6.16) which added the ability to update to Firefox 4.
If you are not running Firefox 3.5.18 or 3.6.16, you will need to update to the latest version first before you can update to Firefox 4. Refer to this guide on how to update:
- Firefox 3.5.17 or older - Update to Firefox 3.5.18 first by going to the Help Menu and select Check for Updates…
- Firefox 3.5.18 - Help Check for Updates… follow the prompts to upgrade to Firefox 4.
- Firefox 3.6.15 or older - Update to Firefox 3.6.16 first by going to the Help Menu and select Check for Updates…
- Firefox 3.6.16 - Help Check for Updates… follow the prompts to upgrade to Firefox 4.
Fresh Install
While the Upgrade Method works most of time, in rare cases Firefox does not properly update. In this case it is best to do a fresh install:
- Go to getfirefox.com
- Click the Download Firefox button to download Firefox 4.
- Close Firefox
- Uninstall Firefox. Note the location specified in the un-installer. WARNING: DO NOT check the box Remove my Firefox personal data and customizations
- Was the uninstall is completed, confirm the location specified in the uninstaller no longer exists. If it does, manually delete the folder.
- Run the Firefox 4 installer.
