Sorry to hear about the surprise. The Old Firefox Data folder is created when Firefox performs a Refresh or "tune-up." Do you recall seeing any dialog/notification about that? Anyway, could you double-click into Old Firefox Data, and then into whatever weirdly named folder you find there, and then into the '''bookmarkbackups''' folder. The creation dates are coded into the file names so you can assess whether this is a fresh folder, or something from a past Refresh. Does this look like the data you want to restore? '''''If so:''''' We can suggest next steps. '''''If not:''''' If you haven't already, could you close out of Firefox and do a normal Windows shutdown and restart to complete any pending updates and release any file locks. If Firefox again starts up without your data, check whether your stuff is available in a different profile, as follows: '''Profile Manager Page''' Inside Firefox, type or paste '''about:profiles''' in the address bar and press Enter/Return to load it. This page should list at least one profile and could list many. (Each profile has two folders and one or more buttons. Do not use any Remove buttons!) The profile that Firefox is currently using will have this: '''This is the profile in use and it cannot be deleted.''' Do you have any other profile(s) listed on this page? If so, you can check whether it is the one you were using recently by clicking its '''Launch profile in new browser''' button. If it isn't what you want, simply close that new window. If it IS what you want, back on the about:profiles page, click the '''Set as default profile''' button for that profile so Firefox uses it automatically at the next startup. Any progress so far?