Running windows 8 as 32 bit? I didn't think that was possible. And why 31.3.0 - that's many months out of date.

Today may be your lucky day. I found another support topic that suggests if you install MoreFunctionsForAddressBook, it can restore deleted contacts.

Does that help? And, you now know the value of timely backups :)

Thanks for your reply. The "MoreFunctionsForAddressBook" installed successfully and it has been able to restore some very old contacts which I deleted a long time ago and had forgotten about. Unfortunately though it doesn't appear to be able to restore entire address books. Neither has it restored any contacts from the rather crucial address book which I deleted. This address book was one of five listed on the left when you go to "address books". Sadly it was the most important. How does Thunderbird store the information in the address books? Is it kept in separate files which mirror the individual address books?. The reason I ask this is because I was surprised that I was unable to find anything in my waste bin when I originally screwed up. I believe the address book which I deleted was originally imported from an .mab file. Re: your technical questions. I haven't updated Thunderbird for some time and am now holding off doing so in case it impairs my ability to recover the deleted information. I am using an Acer Iconia W510 -- a 32 bit machine. Thanks again.

If you deleted the actual addressbook there's nothing that can be done without a backup

Just to confirm then - there's no direct link between individual address books in Thunderbird and individual files on the computer?

Yes there should be. Your contacts will normally (by default) be saved into your Tb profile folder under the name abook.mab. Look under:

Docs and Settings/[your-session-username]/Application data/Thunderbird/Profiles/[arbitrary-string].default/

If you have several address books, you should see several *.mab files.

Thanks for your reply. I found some .mab address books in the directory which you suggested. Sadly none of them appeared to contain the information which I lost. And, as mentioned before, there are no .mab files in the recycle bin. Whatever I did, it was pretty catastrophic. Looks like I'll have to put it down to experience. Thanks again.

You under the misapprehension that deleted files actually go somewhere. They do not. Recycle bins etc are only for files you as an individual manipulate Invented to make people who do silly things safer. And yes I do silly things as well.

There are undelete utilities that can sometime recover deleted files on NTFS partitions. The sooner after the action occurs the more chance of recovery.

There are five free ones discussed here http://lifehacker.com/5237503/five-best-free-data-recovery-tools