I am not aware of any undelete or recovery options for the address book other than the standard undo Ctrl+Z, but that will only ever work immediately after an action.

Thanks, I was afraid of that. I even tried to use my Norton Backup but could not identify the file or folder which contained the address book. I'll have to do it the slow painful way.

abook.,mab is the personal address book... but don't be to sure your Norton product even backs up Thunderbird.... Microsoft promised their transfer wizard transferred your mail and it only does Microsoft Mail programs unless you edit it's advanced settings.