re :''MOST folders seem to be there'' If you used IMAP account then those folders would be on server and so easy to access again. If you had emails stored in 'Local Folders' mail account and you cannot see them. They are stored in the 'Mail'/'LocalFolders' mail account as mbox files. If you can access the old hardrive as mentioned below, you could copy the mbox files (no extension) in 'Local Folders' folder whilst Thunderbird is closed. See image below showing example of mbox files. The mention of ImportExportTools NG is an addon that can be used to import mbox files, but you can copy and paste directly. But at least it shows you what mbox files look like. re: ''however I have no contacts in my address book.Was this data saved anywhere on TB ?'' address books were stored in your 'profile name' folder. address books have a '''.mab''' extension. There are two default address books called 'abook.mab' (Personal Address Book) and 'history.mab' (Collected Addresses). These files can be copy pasted from one profile to another whilst Thunderbird is closed. If old computer died; perhaps motherboard or ram gave up the ghost, but it maybe possible to still access the hardrive to rescue files. Have you tried to see if you can get access to the hardrive itself? You would need to remove hardrive from old computer and connect new computer to it like an external or secondary hardrive in order to see if you get access to files and folders. Worth checking. Default location of profile would be here: C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>\ see image.