Within the C:\Windows.old folder, can you see this: C:\Windows.old\Users\''username''\AppData\Roaming\Mozilla\Firefox\Profiles If you can't get to AppData, turn on viewing of hidden files. This Microsoft article might still work in Windows 10: http://windows.microsoft.com/en-us/windows/show-hidden-files Then when you get into Profiles, if there is only one semi-randomly-named folder, click into that one, then into the bookmarkbackups folder. (If there are multiple semi-randomly-named folders, you'll want to check each for the most recent bookmark backups.) Copy a couple of the most recently saved backups to a convenient location such as the desktop or documents folder. Then you can follow the steps in the following article to replace the default bookmarks with the backup. (Instead of choosing a date from the restore list, use Choose File and point Firefox to the convenient location where you saved the backup file). [[Restore bookmarks from backup or move them to another computer]] Does that work? If you want to do a wholesale restoration of Firefox as it was before, check out the steps in this thread: https://support.mozilla.org/questions/1024189