Uninstall Firefox from your computer {web link}

Download Firefox Full Installer All languages {web link}

If you need more help, or these don't work, ask.for more help. Be sure to describe what is happening.

just uninstalling won't do clean uninstall, if u have corrupted data, depends where it is, it remains in ur PC, if u do simple uninstall like the instructions from that link, so if u do it to solve a issue it won't work cause there is a chance that the corrupted data mite be in a folder or file that uninstall did not remove from ur PC, when u uninstall something, there is always something left behind, in a folder or Reg or both, that what i have learned with using PC

only way for clean uninstall i know is, do clean reinstall to windows, then u can be sure that u got all removed, but its extreme to do it just cause of 1 program