thanks for this, I'll give it a go and see what happens

All of your file handlers will be cleared out. You can get sample download files from:

File Examples https://file-examples.com/

to restore them.

I have installed profiles from Firefox and Thunderbird from my other working machine. It still doesn't work?

GeneWo, I'm suspecting that you might very well have a Registry corruption. Instead of fooling around in the Registry and possibly creating more problems, or having to re-install Windows, I suggest exporting your Contacts from Thunderbird and using a robust uninstaller like:

Norton Utilities 16 (Direct Download Link) http://norton.com/nu16

Norton Utilities 16 is a fully functional, 30-day free trial with an excellent uninstaller. It will create a System Restore point and remove all traces of Thunderbird including Registry entries.

Then reinstall Thunderbird: https://www.thunderbird.net/en-US/

(An alternative to NU16 is BC Uninstaller: https://sourceforge.net/projects/bulk-crap-uninstaller/ It performs the same way but, it's an installed program which always runs in the background (???) If you choose to use it instead, I recommend uninstalling it when you are finished with it.)

Before you decide to do that, do you have any extensions in Thunderbird? Have you tried disabling/removing them?

Never mind. They would've been in your Profile, anyway. Sorry. I'm thinking it all through.

Yes I do, lightning, lt, video downloadhelper

Just so you know I crashed my computer. I'm still reloading it. If that works I'll let you know. Thank you.

Well that fixed it, what a pain reloading. TB68.0