A possibility: - click help>troubleshootinginformation - at 'profiles' in left column, click 'about:profiles' - your old profile may be there. click to launch it and see if the messing folders are there.

Thanks David, does not seem to be there.

Actually when launching Thunderbird do you see a main window like in my joint image, with an "Account Setup" tab asking to "Set up your existing email address" ? If this is not the case please show us a screen shot of your Thunderbird start page.

Thanks Mapenzi. Yes, this did appear and was set up. So mails are being received and sent. However there were many folders for filtered/stored mails received and these have all disappeared.

This is on my better half's computer which is identical to mine and we both use Thunderbird. Mine has worked fine but hers has been a mess with updates.

Thanks Mapenzi. Yes, this did appear and was set up.

What caused this disappearance of your accounts etc in the main window is a corruption of the central file prefs.js in the Thunderbird profile. When this happens TB renames the damaged prefs.js file in prefs-1.js (sometimes invalidprefs.js) and creates a new virgin prefs.js file with a size of 5 to 7 kB which doesn't contain any account informations. So TB starts like after a first installation and asks to set up an email account. This not very rare issue is most times provoked by TB crashes, PC crashes or power failure. I have seen (and treated) this issue a few dozen times in forums but have never experienced it myself.

Do you have a backup copy of your Thunderbird profile folder? In this case you could copy the prefs.js from the backup and - Thunderbird closed - paste it in your wife's actual profile folder. Did your wife use POP accounts? This would explain why after recreating the account only new messages are downloaded.

Thanks, will try what you suggest and report back.