Here's the place to get the latest Firefox: http://download.mozilla.org/?product=firefox-3.0b5&os=win&lang=en-US I don't believe you'll need to reinstall Stumbleupon, but if you have any other addons, they may not be available (which is annoying). I also don't think this version will fix the weird complete-selection-pulldown-menu interface issue that you just have to get used to. (I tried looking for addon/plugin which would fix this, but I am unable to find one.) Anyway, it should be faster and take up less memory than Firefox 2.