If you uninstall Thunderbird via Windows 10 Settings or Control Panel, you will not lose anything, because your profile folder will not be affected. See Profiles - Where Thunderbird stores your messages and other user data

If you use a third-party uninstaller, however, you risk losing your data because they do more than just uninstalling a program. If you have such programs installed, don't use it for Thunderbird's uninstallation.

You can spare yourself any worries by making a backup copy of your profile folder. You should be backing it up anyway, because things can and will go wrong when the opportunity presents itself.

Hi Stans,

Thank you for the advice. I uninstalled Thunderbird through the Control Panel. After the uninstall Thunderbird did not appear in my list of programs on the start menu. However, the shortcut did not disappear. When I hit the shortcut Thunderbird came up? Possibly when the computer repair guy tried to save my programs and data, something got screwed up.

After the Windows 10 control panel uninstall, I downloaded a new version. Wow, it took. I now have the new version 91.8.1. Problem solved.

I guess I shouldn't worry why Thunderbird still came up after the uninstall, at least I am now using the current version? It only appears once in my program files.

Thanks for the advice on Thunderbird profiles in the application data.

Note: I did donate $20 to help support Mozilla.

Installed non-portable programs cannot be backed up and restored like you would do with data. Whatever the repair guy was doing, I sure hope that wasn't one of them. Programs are supposed to be reinstalled, otherwise you encounter strange things such as what you just experienced with Thunderbird. On the plus side, Thunderbird's installation/uninstallation is very forgiving and straightforward, you can even just delete its folder from Program Files and reinstall it, without uninstalling it first.