What happen? When / why did it happen?

Look on your desktop. Do you see a folder called; Old Firefox?

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

Type about:profiles<enter> in the address bar. How many profiles are listed? How many should be there?

Sorry for taking so long coming back. On scanning the computer there is no file "Old Firefox". What happened: On Saturday I woke up the computer from standby and there was a message about there being an update to Firefox did I want to import settings from I think it said Chrome. I don't have Chrome and don't use any other browser so clicked no. Firefox started and didn't have the format I was used to - no header, no bar saying Bookmarks, tools help etc. I just had the tabs and address bar with the icons at the end. I appear to have lost all the add ons, bookmarks, history, no spell checker (it is enabled), no saved passwords, no pinned tabs, I use Onetab and it's gone, and no session manager the box that used to offer reloading the tabs I closed with before (I do usually have a LOT of tabs), I've lost Rapport but I think that may be right. I've checked the links for profile and only one has come up saying .default that dates from Saturday. I'm on Windows 10 and now with Firefox 53.0 (32-bit). I'm sure I was on 64-bit before. I've always sung the praises of Firefox, I'd like to have it back.

You can check if you have orphaned profiles that aren't registered in profiles.ini in the location for the profile folders. A profile needs to be registered correctly in the profiles.ini file to make Firefox recognize this profile.

• http://kb.mozillazine.org/profiles.ini_file

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Go up one level and check if there are other profile apart from the profile you currently use.

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

"AppData" (XP: Application Data; Mac: ~/Library; Linux: ~/.mozilla) is a hidden folder.

• http://kb.mozillazine.org/Show_hidden_files_and_folders