Try using your email to sign in to your existing Firefox Sync account. # Open the Firefox preferences/options window. # Go to the Sync section of the preferences. # Press the "Set up Firefox Sync" button # Press the "Connect" button (under "I already have a Firefox Sync account") # Click on "I don't have the device with me" at the bottom of the window. # Enter your email address in the "Account" box. # Enter your password in the "Password" box. If you don't know your password, just type anything into the box. # Enter your sync key in the "Sync Key" box. If you don't know your sync key, just type anything into the box. # Press the "Next" button at the bottom of the window. If you did not enter the correct password, Firefox will now offer to reset your password. Click on the "Reset Password" link that appears after you press "Next." When your password is correct but your sync key is not, then Firefox will offer to reset your sync key. Click on the "I have lost my sync key" link that appears after your press "Next." Then click on the "Generate" link next to the displayed sync key. Then press the "Change Sync Key" button.