Try reinstalling the Visual C++ Redistributable.

Disable any third-party antivirus or security software. Reboot in Windows Safe Mode and see if it still crashes there.

You can test older versions with mozregression to see if it worked previously and find the change responsible.

Reinstalling Visual C++ Redistributable or disabling anti-virus didn't allow Firefox to start.

Firefox still crashes in Windows Safe Mode.

I used mozregression, but I am not really sure what the results mean. I set the "bad build date" to yesterday when it first started crashing and the "good build date" to the day before. Everytime mozregression started Firefox, it started (but didn't have my normal startup screen. I think it lost connection to favorites, home page, etc.). Please see attached screen shot.

Thank you for your reply and help.

What version of Firefox? Some process is causing the issue and you need to investigate what's running on your computer. I suggest you get the below tools and see what's running when your computer starts. https://learn.microsoft.com/en-us/sysinternals/downloads/autoruns

This tool will allow you see who the processes belong to. https://learn.microsoft.com/en-us/sysinternals/downloads/process-explorer

Hit YouTube and see the tools in action. You can also join the rest of us and run Linux.  ;-)

Another suggestion would be to buy another drive and a external case that works with your drive, clone your current drive to the new drive, install the new drive in your computer and then reset windows and start over. You will still have your data on your old drive in the external case. Sorry, but just a geeks mind running wild  ;-))

I don't know what version it was when it first started crashing, but I have since downloaded and installed the latest version (120.0) as part of the troubleshooting process.

I took a look at some of the tools you suggested and I am not sure how I would use them to determine a problem with Firefox starting. It seems a little beyond me.

Thanks for your help.

You can create a new profile as a quick test to see if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

If the new profile works, you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile