Do you have an Old Firefox Data folder on the desktop?

No i don't. My data just flat up diseapered. i i didn't refesh it either. i was just getting rid of pesky windows update assistent.

Could you first shut down and restart Windows? Sometimes at startup Firefox isn't allowed full privileges and your data is inaccessible.

If Firefox remains uncustomized after that:

Search for Other Profile Folders

Does the Profile Manager list your immediately previous profile folder?

To check on that, inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list all the profiles Firefox is currently aware of. If you see a profile that is not currently set as default that looks promising, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but I think those are still "under construction" so please ignore them.)

Firefox should exit and then start up using the other profile. Is that the right one?

If it's not there...

Did Firefox orphan your old profile folder?

Here's how to check whether there are additional profile folders in the standard location in addition to the one you're using. Start by opening your current Firefox profile folder using either:

* "3-bar" menu button > "?" button > Troubleshooting Information
* (menu bar) Help > Troubleshooting Information
* type or paste about:support in the address bar and press Enter/Return

In the first table on the page, click the "Open Folder" button, to launch a new window listing various files and folders in Windows Explorer.

In the Windows Explorer address bar, click the capitalized word Profiles to move up one level in the folder hierarchy. More than one folder here by any chance? Do the files in those folders look like they were last updated around the time of the update?

If you've got any promising looking folders, we can discuss next steps to recover use of them, or at least your bookmarks.

Mine Other Restore Points

Windows may have your more recent system state, either with actual data in the Old Firefox Data folder, or in your Profiles folder. On Windows 10, I suggest investigating this way:

(A) Set Windows to show hidden files and folders

https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

(B) Download the System Restore Explorer tool

http://nicbedford.co.uk/software/systemrestoreexplorer/

That program shows you files and folders in restore points. If you have a more recent one, you can look under:

• \Users\username\Desktop\Old Firefox Data
• \Users\username\AppData\Roaming\Mozilla\Firefox\Profiles

You can try saving out a recently modified profile folder to a neutral location and mine it for files. See: Recover important data from an old profile.

Dude, thank you so much! i've used the "about:profiles" methed and vollia!!! My old glorious was sitting there, knocked of its feet by the treachous, default profile enity!!! But thanks to your support, i found it, and restored it, along with it amazily outdated extenions, 2 or 3 translaters, and a glorious Firefox theme of an anime sniper girl that i don't know if shes from an real anime or just a fan made up one, since i just a casual anime watcher. i congratulate you dear sir, for i was feeling hopless, thinking i had to rebuild my way up, just because of some unknown incdent. Anyway, my original profile and i shall go and search for the heretic spy that violated my rightful profile and replaced it with the inferior default one(though without it i couldn't contact you and would had to use chrome, which isn't bad but i jst refused to truly believe my data would just 'cease to exist like that.)!!! Anyway, thank you for your help!!!

P.S Oh, also i thank Mkll for also a suggestion as well.

P.S.S i just finished "Darker Than Black" so know i'm level 3 in my 'Ame' stat.