If you recently changed over to the faster 64-bit version of Firefox, it's likely that the 32-bit version is still sitting on your computer. Simply remove the 32-bit version of Firefox from your computer and you should be all set to go. In Windows 10, if you go to the '''settings''' and select '''apps''' you will see all programs installed on your computer. If you truly have 2 versions of Firefox installed on your computer, you should see '''Mozilla Firefox''' listed twice. One version should have '''x64''' at the end of it and the other will either say 32-bit, x86 or nothing at the end. Delete the one that doesn't have x64.