I would like to completely uninstall Thunderbird from her computer, including all the old files and database(s).

You're wasting your time. What is your anti-virus software?

Hello there glindathegood. We have read your message we try to help you.

Hello there .

Do you really want to remove all files from the computer? And install a fresh install on your mother's pc machine again? Have you had permission for that? well okay.

Greetings Firefox Volunteer.

Delete.

You say I am wasting my time

Profile files are stored separately from the Thunderbird program files. The program files are static and do not change (except when you upgrade the Thunderbird application version). Because we store profile and program files separately, you can uninstall Thunderbird without losing your messages and settings, and if something goes wrong with a Thunderbird update your information will still be available. It also means that you don't have to reinstall Thunderbird in order to delete your information or troubleshoot a problem.

... antivirus software is Avast.

Try to start Windows in safe mode with networking enabled.

Still in Windows safe mode, start Thunderbird in safe mode. Does the problem go away?

Hello there again Glindathegood.

⚫️ to really install Thunderbird I have a video and list for you. If you follow this then you will be fine. about installing Thunderbird. https://support.mozilla.org/en-US/kb/installing-thunderbird-windows

⚫️ To uninstall Thunderbird. http://write.flossmanuals.net/thunderbird/removing-thunderbird/

⚫️ This is where Thunderbird has or hide there stuff. http://kb.mozillazine.org/Installation_directory

Greetings The Firefox Volunteer

Hello there again

This where Thunderbird hide there stuff if you want to know where that is. http://kb.mozillazine.org/Installation_directory

Greetings Firefox Volunteer.

Delete.

Cymo, thank you - those links look helpful! I appreciate them.

I don't know how to do safe mode, networking settings, etc.

You could simply click on the provided links.