Unless you have a copy somewhere . . . . . . . . .

Do you recall any questions posed by the installer about what to do with the data that was already on the hard drive? Some options may lead to a special folder being created.

To explore, you'll first need to turn on viewing of hidden files and folders: http://windows.microsoft.com/en-us/windows/show-hidden-files

Then check here:

C:\Windows.old\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles

Assuming you find one or more folders there, one of them most likely will have your earlier Firefox data. Any luck?

If that doesn't exist, try a global search of your "C" drive for bookmarkbackups which is a standard Firefox folder. Hopefully you'll find more than just your new one.

jscher2000 said

Do you recall any questions posed by the installer about what to do with the data that was already on the hard drive? Some options may lead to a special folder being created. To explore, you'll first need to turn on viewing of hidden files and folders: http://windows.microsoft.com/en-us/windows/show-hidden-files Then check here: C:\Windows.old\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles Assuming you find one or more folders there, one of them most likely will have your earlier Firefox data. Any luck? If that doesn't exist, try a global search of your "C" drive for bookmarkbackups which is a standard Firefox folder. Hopefully you'll find more than just your new one.

I did that, and the bookmarkbackups that appeared were the new sync. ones and before tat I didn't find the windows.old folder even after showing the hidden folders

Is there any hope or they are gone for good?

It's hard to hold out hope. You could try an "undelete" program like Recuva and look for any recoverable files that match the pattern

bookmarks-2016-04 ... .jsonlz4

https://www.piriform.com/recuva

(Corrected per the following reply)

Note that the bookmark backups have a .jsonlz4 file extension (.mozlz4 is used for search.json.mozlz4).

• bookmarks-YYYY-MM-DD_<item-count>_<hash>.jsonlz4

• https://support.mozilla.org/kb/restore-bookmarks-from-backup-or-move-them
• http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox

For future prevention, see:

• https://support.mozilla.org/kb/Backing+up+your+information
• http://kb.mozillazine.org/Profile_backup