Export the hotmail contacts as a .csv file and save to your desktop. If you wish you can open a .csv file using eg: Excel or OpenOffice calc You can edit the column heading to match those of Thunderbird. See info at link: * http://kb.mozillazine.org/Import_address_list_from_text_file then Import the .csv file. In Address Book Tools > Import Select : Address Book and click on Next Select: Text file (LDIF, .tab. .csv, .txt) and click on Next you may have to map the column headings.

https://support.mozilla.org/en-US/questions/1012084#answer-607601