These computers usually use Xandros, which is a version of linux that is no longer actively developed. Unfortunately I don't think there is a good way to update Firefox on these machines. I'd suggest you install a new version of linux (Ubuntu is a very popular and easy to use one). This is a bit beyond the scope of this forum however, I'd suggest looking on a few linux forums. They can help you find a version of linux that is more modern, faster and more secure, and then help you with installing it and setting it up. You'll be able to use the newest Firefox at that point, plus your operating system will be updated and faster.