Hi Andis. First of all, this is completely normal behavior, although it's a bit irritating, I know. What happens is that when you close Firefox, despite the window disappearing right there and then, Firefox keeps running for a little bit until the whole closing procedure is completed. This can take a fraction of a second on fast computers, or can take a few seconds on slow computers or when Firefox is storing a large session (if you save your tabs). All you have to do is wait a bit until Firefox closes, and then open it again. To see if it's still running, you can press CTRL+SHIFT+ESC and then, under the Processes tab, you can see if firefox.exe is still there. If it's taking an unusual amount of time to close (which happens very rarely, and only if the browser freezes on exit), you can force the application to terminate from this application (task manager). Firefox 4.0 will reduce by 97% the time it takes firefox.exe to close, so this problem will be basically erased for Firefox's next version. Until then, I can recommend you this extension, which helps you restart your browser more easily and without bothering about closing times: https://addons.mozilla.org/en-US/firefox/addon/3559/ Hopefully this will help.