HELP question continued - If I click on an email address in (for instance) a word doc or an excel spreadsheet, a highlighted email link, then it opens (like normal) as if to write an email... and I can then (in the 'To' box) type any letter (a to z) and still all my previous email addresses come up as options - so it looks like it has the memory of all my email contacts and email addresses.

   But it won't let me type anything in the 'Body Text' and it won't let me send any email (if I put in an email address and a subject).
   If I click 'continue in troubleshoot mode' then it just goes back to the "Welcome" and "Account Setup" pages.

click the windows icon in task bar. On the window that opens, enter run and press enter. That opens a small command line window. On that, enter thunderbird.exe -p and press enter. That brings up the profile manager. Click 'create profile' and browse to and select your profile which is probably at c:\(your name)\appdata\roaming\thunderbird\profile with a name such as 123456.default. If there is more than one folder there, pick the larger one. Give it a name within profile manager and continue to TB. All should be okay.

Hello David, Thanks for your help. I am following your instructions but I'm very nervous about doing anything wrong and losing or corrupting anything. So when I click 'create profile' it brings up a window 'Completing the Create Profile Wizard' which has a box to 'Enter profile name:' which already has 'Default User' typed in it (but it looks like I can change it if I want). It also shows the location as: C:\Users\(my first name only)\AppDate\Roaming\Profiles\(eight characters/numbers).Default User

[I've added another image (screen grab) of the 'Completing the Create Profile Wizard' window, and painted red over the name parts]

It has a button 'Choose Folder...' that I can click. It also says "Click Finish to create this new profile" with options 'Back', 'Finish' and 'Cancel'. There is another button 'Use Default Folder' but it's not active.

So, do I leave the profile name as "Default User"? When I click 'Choose Folder...' there is only one folder '(eight letters).default', but it has lots of folders inside it (and one of them is 'ImapMail', so I guess that means it is 'IMAP' and not 'POP' (not that I have any idea what they are, but someone asked me which it was).

When you say "give it a name within profile manager" do you mean to rename the folder? Or in that box to 'Enter profile name:' do I give it a name there? And what sort of name, just my name?

I have three email addresses that have always been visible in the one Thunderbird function, will they all still be there, and all their history (from the last ten years) too? Sorry for all the dumb questions (you're obviously very tech-savvy and I'm almost a Luddite, ha ha), I just really have no idea what all this is (computers might as well work with 'magic' as far as I'm concerned), etc, and I am really worried about losing anything. And why did this change/problem occur at all when it was fine a couple days ago?

You want the folder with the long name... xxxxxxxx.default The profile manager does not change anything, it just sets a pointer to your preferred profile. I suggest giving it a name so you will know it's the right one in case this happens again. Nothing in these steps changes any content in the profile. That panel for 'completing the profile wizard is where you can overtype the assumed name of 'defaultuser' with DARRENSPROFILE or whatever. It's just a memory jogger to assure you in the future. On your other question, yes, there are many subfolders and they are part of the profile - do NOT touch them.