There is talk of ending Windows 2000 support starting with Firefox 8. This is in part due to move to MSVC (Microsoft Visual C++) 2010 based compiler which requires Windows XP SP2 or newer OS. Firefox 8 is now on the Nightly Branch is scheduled for release on November 8, 2011. Also, there is chance 64-Bit Windows support may be coming with Firefox 8. We will post more about this as more information is released.