you can export an addressbook, but (to my knowledge) not a distribution list. you can import the full addressbook with tools>import>import from a file and follow the links for addressbook. when you get to last menu, it will offer several addressbook formats to import. To know which one to use, check the profile of old laptop's thunderbird. if there is an abook.sqlite file, then on new computer, import the abook.sqlite file. If not, then import the abook.mab file (which is the older version)..