This is probably not due to anything you did intentionally.

To confirm which Firefox you are currently running, check the Troubleshooting Information page. Either:

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

In the first table there should be a row for "Application Binary" which shows the path this instance of Firefox started up from. It also should have a Profile Folder row showing which profile you're using (presumably the one you want to keep using after the cleanup).

Have you encountered any situations in which external links or shortcuts trigger the other installation of Firefox? If so, the first thing would be to temporarily switch your default browser to Internet Explorer or Edge so that removing an unwanted installation doesn't break that setting.

Thanks for your response. As I stated, the one is in program files folder, the other in program files (x86). They both open up in their separate folders. I know this because I see the usual website I go to when I open up the one and the other opens up without any evidence of use.

So how do I uninstall one and not the other? I would like to save the install of the one that has my previous history if I can. I think that one is in the (x86) folder.

If this scenario is caused by onedrive syncing, I am afraid this will happen again. The solution may have to involve my other PC.

It might be best to just delete the unwanted folder as an uninstall may remove the wrong data.

Yes, I think manually deleting the unwanted program folder is simplest BUT first you want to confirm which one is the one you normally use AND make sure that the default browser setting is not broken.

What is the role of OneDrive? Most likely it is not pointed at the program folders. Is it backing up your Firefox profile folders?

As I stated, the one is in program files folder, the other in program files (x86). They both open up in their separate folders. I know this because I see the usual website I go to when I open up the one and the other opens up without any evidence of use.

Each installation is using a different profile folder -- that is why they have different customizations. Profile folders are stored under C:\Users\username\AppData\Roaming and not in the program folder.

Please see my first reply regarding sorting out which is your preferred Application Binary and Profile Folder (you'll see the full path).