Not sure what you are trying to achieve so mention several options for you. '''How to open the Address Book:''' The 'Address Book' button should be on the 'Mail Toolbar' along with 'Menu icon' , 'Get Messages' and 'Write'. If it is missing: Right click on the 'Mail Toolbar' and select 'Customise' If in list, drag and drop onto the 'Mail Toolbar' or click on 'Restore Default set' button. click on 'Done' button '''How to export my address books to use as eg: backup.''' * Open 'Address book' * select an address book (not 'All Address Books' as it is a virual address book) * 'Tools' > 'Export' a window opens * choose where to save the file. * Give file a suitable name. Either save as LDIF or 'CSV * Save as LDIF is easy to reinstall. * Save as 'Comma Separated .csv file' - .csv files also easily imported but also you can open those files using eg: MS Excel. * click on 'Save' button. '''Where are my address books in my Profile name folder?''' Profiles are with the Appdata folder, so may be hidden. Make hidden files and folders visible: * http://kb.mozillazine.org/Show_hidden_files_and_folders To access Profile name folder whilst Thunderbird is closed and assuming it is in the default location: * C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>\ To access Profile name folder via Thunderbird: * 'Help' > 'Troubleshooting Information' Under 'Application Basics you should see 'Profile Folder' listed * click on 'Open Folder' a new window opens showing the contents of your 'Profile name' folder. If you intend to backup or modify anything, you must '''exit Thunderbird now.''' Address Books have extension .mab 'Personal Address Book' is called 'abook.mab' 'Collected Addresses' is called 'history.mab' These are the default address books. Any other address books eg: 'abook-1.mab' will be ones you have created. If you want to backup the entire profile, go up the directly and copy the 'xxxxxxxx.default' profile name folder. Profile location info: http://kb.mozillazine.org/Profile_folder_-_Thunderbird