As per their FAQ: ''''''I’ve lost my reminders! Can I retrieve a backup?'''''' Reminderfox stores all reminder/todo’s data and backups in one directory. With a typical installation that directory is part of the users “profile” directory. Examples See also in Options. Windows XP: C:\Documents and Settings\Administrator\Application Data\Mozilla\Firefox\Profiles\{someRandomNumber}.default\reminderfox\ Windows7: c:\Users\{username}\AppData\Roaming\Mozilla\Firefox\Profiles\{someRandomNumber}.default\reminderfox\ Linux: /home/{username}/.thunderbird/{someRandomNumber}.DefaultUser/ The reminders and todos’s are typically stored to that directory with a file named “reminderfox.ics”. For that “reminderfox.ics” file automatic backups (snapshots for today and yesterday) are kept with a .bak1, .bak2, or .bak3 extension. Example c:\Users\{username}\AppData\Roaming\Mozilla\Firefox\Profiles\{someRandomNumber}.default\reminderfox\reminders.ics.bak1 '''Find an old / previous used “reminderfox.ics” file''' Sometimes it’s necessary to find a previous used reminderfox.ics file — like in situations when a new profile for Firefox/Thunderbird has been defined, or where the Firefox/Thunderbird profile is defect or lost — then it can help to search the disc for Reminderfox files like reminderfox.ics or just with *.ics or some of the backup files like *.bak1. To use a reminderfox.ics file found in an old profile, first check the file size and the date stamp. If a “good” version is found, copy that reminderfox.ics to your desktop (also for backup purpose) and then import it using the Reminderfox Options tab:File. www.reminderfox.org/documentation-faq-troubleshooting/#r5