Actually, there is more than one option, but I'll respond to your request. - click help>troubleshootinginformation - scroll down to 'profile folder' and click 'open folder' - exit thunderbird - IMPORTANT - back up one folder so that you are out of the profile - copy and paste that profile to the other drive. - restart thunderbird - click help>troubleshootinginformation - scroll down to 'profiles' and click 'about:profiles' - click 'create profile' - click next - create a short nickname for account and click the 'choose' button to locate and select your profile on the other drive - click finish and launch the new profilelocation.