Windows XP with Service Pack 2 is the minimum Windows version that meets the Firefox System Requirements. We'll explain how to find out your Windows XP version and what to do if you're using Service Pack 1 or below.
If it says Service Pack 2 or Service Pack 3, your Windows system meets the requirements for the latest version of Firefox.
If it says Service Pack 1 or nothing at all, your system doesn't meet the Firefox system requirements. The only popular web browser that is still being updated with security patches for older versions of Windows XP is Opera.
To download and install Opera, visit the Opera website.