Had a Firefox account for many years but didn't know which email account it was registered to. Now have just retire old iMac and purchased new one. Firefox wouldn't run on the old one so threw it away. Now i've registered under another email address and find that I have two accounts using the same password. Then sign up iPhone on the second account and things are going to get crazy if i don't stop one of these accounts, preferably the second new one in favor of the old one. Help!