If the file is abook.mab or history.mab (Personal Address Book and Collected Addresses, respectively), you can overwrite the existing version of the file in your profile folder. Select Help/Troubleshooting Information, click Show Folder to open the profile folder in Explorer, exit TB, then copy the .mab file into the folder. When you restart TB, Address Book will display the contents from the older computer.

If it's a non-default mab file, e.g. impab.mab, you will have to import it with the help of MoreFunctionsForAddressBook.

sfhowes Your response was helpful in that it made it clearer to me how I should go about doing this. However, when I did as instructed, it ended up without actually opening the address book. I could see the file in Explorer in the Thunderbird folder and clicked on it and it goes immediately into a new email as an attachment. Color me confused, once again. Sorry to be so silly or obtuse, but is there something obvious to you that I am doing wrong? I really do appreciate this help because it made the functions clearer to me & gave me more understanding of the program. Smiles, Shurrwill

After you copy abook.mab into the profile folder, overwriting the existing file, restart TB and click on the Address Book icon on the Mail toolbar (or press Ctrl-Shift-B, or click the AppMenu icon then Tools/Address Book). This will 'open' abook.mab.

sfhowes, Thanks very much for all your help. I still have not been able to make it work & I am not really sure what I am doing wrong at this point. <Sigh> Really want to find all this stuff, but I guess I will have to rebuild my address book. Unfortunately, all my passwords were in there as well. Oh well, that is what I get for not simply printing the damn list, right?  :) Thanks again! Shurrwill

I suggest you go into the file association in windows control panel and remove the file association you made for MAB files.

Note here that until your fix the mess you made in file associations, double clicking an MAB file will see stupid things happen.