They are probably not lost.

First, I recommend backing up your Firefox settings in case something goes wrong. See Backing up your information. (You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder.)

Next, try restarting Windows to release any file locks that may be preventing access to your original profile folder.

When you get back to the desktop, try firing up the Profile Manager and see whether you can choose your old profile (usually named something like gibberish.default): Managing profiles.

Does that let you return to normal operation?

If not, the following article has suggestions for recovering bookmarks: Lost Bookmarks | Troubleshooting | Firefox Help..

You either have your bookmarks or you don't in your profile changing the version won't change things.

Assuming you do not see your bookmarks om

• Bookmarks Toolbar
• Bookmarks Menu
• Unsorted bookmarks

Bring up your profile in Windows.

1. "Alt+H" (Help) > Troubleshooting information >click on "Open Containing Folder"
2. you are now looking at your profile in Windows
3. note the filename
4. go up one directory, to see if there are other directories

If you have multiple directories check out the dates in each for last updated date timestamps for places.sqlite and inside bookmarkbackups folder for individual .json files. You may find from the dates that you switched profiles.

If you find one then note its filename (the profile name is part of the filename) and then start the Firefox Profile Manager and open with that profile.

To prevent the problem in the future don't let Firefox start up for you after downloading and installing a new version. Instead exit the install at that last point, and restart Firefox in your normal manner.

Lost bookmarks - MozillaZine Knowledge Base

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

If this does not lead to a solution what version were you on when you updated, how did you update (asked to update or went to mozilla.com)

Sorry about leaving out a step, another method of opening the profile folder -- this one does not involve menus (ref: Q841635 Not saving History)

1. type about:support into the location bar
2. click on "Open containing folder" button:
3. you are now looking at your profile in Windows
4. note the filename
5. go up one directory, to see if there are other directories

Sorry, but I'm already lost. I can't find "Open Containing Folder."

A possible cause is a problem with the file places.sqlite that stores the bookmarks and the history.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox

Help > Troubleshooting Information > Profile Directory: Open Containing Folder

Too many self proclaimed experts!

Simple:

Open your newly upgraded Firefox, Click up near the top on the Menu Bar, on "Bookmarks" (if the MENU BAR is not present, right click to show it), then click "show all bookmarks", then click "Import and backup" which will produce a drop down menu, choose "Restore", then pick the date of the last known time you knew your bookmarks were good. Done.