Windows may move your personal data to a C:\Windows.old folder. If you have this folder then you can recover some specific data. You can copy files like these with Firefox closed to the current profile folder to recover specific data. Note that you should be cautious with copying SQLite database files if you previously had problems. *bookmarks and history: places.sqlite *bookmark backups: compressed .jsonlz4 backups in the bookmarkbackups folder *cookies.sqlite for the cookies *formhistory.sqlite for saved form data *logins.json and key3.db (decryption key) for Passwords saved in the Password Manager *cert8.db and possibly cert_override.txt for (intermediate) certificates stored in the Certificate Manager *persdict.dat for words you added to the spelling checker dictionary *permissions.sqlite for Permissions and possibly content-prefs.sqlite for other Site Preferences *sessionstore.js for open tabs and pinned tabs 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:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox