What's your computer system and Firefox version? Did the error say all files, some?

uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. (Note : this should be pinned and run weekly, if not done below ever then there are 100's of gigs) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles Reinstall with Current Release Firefox 57.0.2 with a Full Version Installer https://www.mozilla.org/firefox/all/ If still have issues : Please try this and make a new Profile : https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile Please keep Video Card Drivers update, very important. Thank You Please let us know if this solved your issue or if need further assistance.