First, let's make sure your system is clean.

You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

Ridewith said

Firefox will not open

Please explain the problem in detail. What happens? What is the exact error messages?

Hi Ridewith, do you get a specific error message when you try to start Firefox? We may have an article on that or a fix for it.

Ridewith said

Any way to find my bookmarks?

Can you search for your Firefox data folder this way:

Select and copy the following shortcut path:

%APPDATA%\Mozilla\Firefox\Profiles

Paste that into the Windows 10 system search box or into the Run dialog (Windows key + R will call that up) and press Enter to load it. That should expanded to this hidden path:

C:\Users\username\AppData\Roaming\Mozilla\Firefox\Profiles

Here you will find one or more folders, each of which is a separate Firefox profile folder. The naming scheme has a random part, then a dot, then a more readable part, like

a12bc3d4.default

Each profile folder should contain a bookmarkbackups folder. The files in that folder will have the date and number of items coded into the names. These can't be opened directly by other programs, they are meant to be restored by Firefox.

If you found a bookmark backup file that you want to use:

I do have a tool to convert them to an importable HTML-format file if you want to see what is in the backup file before restoring it.

• Restore feature: Restore bookmarks from backup or move them to another computer
• Converter: https://www.jeffersonscher.com/ffu/bookbackreader.html
• Steps to import an HTML-format bookmark file: Import Bookmarks from an HTML file

If you did NOT find a bookmark backup file that you want to use:

We'll have to suggest next steps.