Hi Samenater, yes, usually you can remove the unwanted version pretty easily. Does the Windows 7 "Add/Remove Programs" control panel list both of them separately? If not or if it's not clear, each program folder contains an uninstall folder with a program named helper.exe.

Two Important Things

(1) If the uninstaller asks whether you want to delete your data or profile, tell it No.

(2) If you have an installation of Microsoft Office, make sure it is using Firefox 89 before uninstalling the older version. Office can be extremely stupid about removal of what it considers to be the default browser.

Note that it is possible that there is only a leftover orphaned entry present in the Windows Registry and that there is only one Firefox version installed. In this case if you remove the older version then you actually remove the current version and you would have to reinstall Firefox. So make sure you you verify that you actually have two version installed in different program folders.