hello paisley157, this error might be caused by security programs such as zone alarm - please temporarily disable those programs for the following procedure: *download the full firefox setup file from getfirefox.com *uninstall firefox on the machine (but don't chose to delete your custom files & settings in the uninstaller!) *manually delete all remaining files in the firefox program folder, which usually resides in ''C:\Program Files (x86)\Mozilla Firefox\'' *reinstall firefox