Running Firefox 3 on Win2k is great! To me one of the selling points of Firefox is that it runs on older OSes, reducing the need for upgrading older machines and thereby saving money!
Of course if you think that is something, I have had Firefox 2.0.0.x running under NT 3.51 - for which there was NEVER a native 32-bit version of IE available. Screen shot: http://toastytech.com/guis/ff2nt351.png