Hello frenchdragon, see : [https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles#w_backing-up-your-profile Backing up your profile] and then [https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles#w_restoring-to-a-different-location Restoring to a different location] . For more information see: http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox thank you

Note that because the folder organization on Windows XP and Windows Vista and later is quite different it is better not to copy the full profile folder content, but only copy (SQLite) files that you really need. For passwords you need the signons.sqlite and key3.db files. Extensions are best be reinstalled to ensure they are initialized properly.