We strongly advise our users to upgrade from Firefox 3.6, as they will no longer receive critical security updates as of April 24th. In support of Firefox 3.6 users in organizations, we've delivered on our promise to implement the Extended Support Release plan three months ahead of ending support for Firefox 3.6. Enterprises and organizations should complete qualification and deployment of the ESR over the next month.
We'd also like to take this opportunity to announce that our minimum supported Windows version will change from Windows 2000 to Windows XP SP2 in Firefox 13. We never change minimum requirements lightly, but this support change allows us to significantly improve Firefox performance on Windows by using a more modern build system. Windows XP users are advised to update to the latest service pack, and Windows 2000 users should consider upgrading ahead of the June release of Firefox 13.
Happy to try to answer any questions you have. Oh, and if you're a Windows 2000 user and you simply cannot upgrade your PC to a more modern Windows version, I'm sure the good folks over at Opera will be happy to help you out. Moving to Opera means you'll not only get continued security updates, but you'll also be able to enjoy a modern browser experience.