Yes, you can remove all those orphaned entries under the Uninstall and the Mozilla registry key and only keep the key for the version(s) that are still installed. It happens a lot that when you update Firefox that the updater doesn't remove the old entry, but only adds a new entry for the new version. If there is only one entry to the Firefox program folder but with a wrong version then leave that entry or edit it to reflect the currently installed version.

HKEY_CURRENT_USER\Software\Mozilla
HKEY_LOCAL_MACHINE\SOFTWARE\Mozilla
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Mozilla Firefox (????)

Thanks for that. Will do :}