You seem sure about giving Thunderbird a clean slate, so I will give you instructions to do that, rather than try to troubleshoot whatever is wrong with Thunderbird on your computer.

Yes, you can backup the information you have in Thunderbird. You can adapt my instructions: Create a clean new profile in Thunderbird and import your stuff from the old profile.

Once you have backed-up or copied that Profile folder, then have exported data from Thunderbird using my instructions above, then you should quit Thunderbird and delete that original Profile folder from your computer (not your backup of it!). Then uninstall Thunderbird.

I recommend that you use Revo Uninstaller Freeware (scroll down the page to see the free version). Use it to uninstall Thunderbird, then have it do its extra steps (Advanced scanning mode), to find and remove anything left behind.

Once you have the program uninstalled and have deleted the profile folder (but not your backup!!!!), then use Disk Cleanup (type "disk cleanup" in Cortana search to find it). Then use CCleaner to cleanup things from your computer.

Then reboot the computer! This is an important step.

After the reboot, install Thunderbird again Download & install Thunderbird

Then continue with the instructions from my webpage for creating a new Thunderbird Profile (I recommend creating one that does not have the name "default" or "default user", as there have been problems sometimes with this).

Then continue with my instructions for importing your stuff into Thunderbird.

If you need/want any clarification or more details with any of this, let me know.

Your downloaded mail, settings, address books, add-ons, saved passwords etc. are stored in a "profile" directory. Uninstalling does not delete that profile. If you re-install Thunderbird will automatically reuse that profile.

See http://kb.mozillazine.org/Profile_backup if you want to backup the profile beforehand just to play it safe.

I suggest you add a Gmail IMAP account and see how well that works. That will help you determine if the problem is your ISP's mail servers (most ISPs are poor email providers since they view it as just a cost center) or something generic . See http://kb.mozillazine.org/Gmail if you want to do that. Its useful to have a second account for troubleshooting, and as a backup in case of problems.

If you have problems with the Gmail account too, see http://kb.mozillazine.org/Performance_-_Thunderbird

However, if the entire PC freezes (not just Thunderbird becoming "non-responsive") then I'd look elsewhere. I'd start by running windows update, updating my graphics driver and see if booting Windows 10 in "safe mode with networking" makes a difference. If safe mode makes a difference that implies you have a windows driver problem. See https://answers.microsoft.com/en-us/windows/forum/windows_10-performance/boot-windows-10-in-safe-mode/493f8033-43d3-495e-9421-758eb46df1db if you want to do the latter.

If you really want to start over cleanly with Thunderbird, do not let it use the old profile. The profile could have problems with it.

I can give lots of instructions about what to do if there are problems with Windows (I'm a Windows computer tech), but since your question was focused on reinstalling Thunderbird, I figured to help with that.

I really think you ought to run a Check Disk, though.

If you having problems in Windows, not just Thunderbird, then you should definitely address them. A whole computer freeze-up is often caused by file system errors or bad clusters on the hard drive (which a thorough Check Disk will help with), though a bad display driver can cause it also (just not as often, in my experience).

What else that could be done to fix Windows would all depend on exactly what goes wrong and when.

Thanks to you all......... I follow Bruce's instructions (Sort of) and deleted TB from my computer after I made a "Profile back-up" on a USB stick. I used a couple of different tools because I had them handy and it seems to have worked fine..... Re-installed TB from the website and it simply backed up the profile as it installed :-) I have my fingers crossed that it will remain gremlin free going forward....TB worked fine for short periods before...I am hoping this is an actual FIX not just another period where the gremlins are sleeping and waiting to attack again. Thanks again

Obviously I spoke too soon.......... as I said above I did the full delete/reinstall and it worked fine .... at least for a few hours!! It is right back to where it was before all the screwing around....turns out it was a total waste of time.........Thanks anyway guys. Solution is obviously to find a reliable e-mail client and leave this nonsense behind....there must be one out there that actually works.... I hope :-(

Did it occur to you that the problem may be outside of Thunderbird? Since you virtually gave no details about your problem(s) I'm not going to speculate, however, anti-virus software seems the most likely culprit to me. Since you already marked this topic as 'Solved', you can start a new topic and provide more detailed information about your problem.

Sounds like when Thunderbird was installed again, it used the old profile folder, which I warned about.

As you say, you "sort of" followed my instructions. So it "sort of" didn't work.

At this point, I cannot possibly know what you did, so I cannot possibly know if the problem is in Thunderbird or Windows.

If you want to try using another e-mail program, that's fine, but if your problems are in Windows, you are just going to have more problems. When that happens, please find a Windows computer tech near you to take your computer to, to get fixed.

Turns out the problem was in Thunderbird....basically what I guess is a corrupted profile. Anyway, I got a local techy to help me and it is all solved now..... Thanks to you all for your help.