Can you recover the Old Firefox Data folder from the Windows Recycle Bin? (If necessary: [https://support.microsoft.com/en-us/kb/810869 How do I make the Recycle Bin appear on my desktop in Windows Vista or in Windows XP?]) If that doesn't work, you could try an "undelete" tool such as this: https://www.piriform.com/recuva -- that sometimes works Here are two things to try: The following article has the steps to call up the Restore feature. If backups are available in your current Firefox profile (settings) folder, they should be listed by date: [[Restore bookmarks from backup or move them to another computer]] ''If you get your Old Firefox Data folder back:'' Try restoring a bookmark backup from the Old Firefox Data folder on your desktop. Check inside for a semi-randomly-named folder and check inside there for a folder named bookmarkbackups. If you have that, please use the article under #1 above but use the "Choose File" option to restore one of the backups from the folder on your desktop. Any luck?