You don't need all of the Roaming\Thunderbird folder, just the Profiles subfolder is enough. Inside this, you will find the actual profile folder named something like xxxxxxxx.default, so the path of the folder whose contents you need is Roaming\Thunderbird\Profiles\xxxxxxxx.default

A link to the instructions you followed would be helpful so that we know what you're doing. Also, make sure Thunderbird is not running when you copy the profile folder from the source computer to the destination computer. See https://support.mozilla.org/en-US/questions/1289124?utm_campaign=questions-reply&utm_medium=email&utm_source=notification#answer-1318119

Thanks for that Stans - I am following these instructions - https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer. I followed them more easily on this new PC as it showed me a video that I could check against. To someone unaccustomed to the program info mentioned in the directions there was insufficient detail to be sure the correct actions were being taken - and nowhere did it say I just needed the Profile subfolder. I made sure that I turned off Thunderbird as per the directions - though fathoming all that out took me the first 3 attempts to be sure I'd got it all correct. I will now follow those instructions that you kindly gave a link for - and I'll report back. John

Stans, I'm afraid I'm a bit confused with this. Is this starting from the original PC? If so then I have actioned everything in your first paragraph - but now the terms you use are strange to me. I'm using an old hard drive in a powered caddy as my back up area, so do I now copy all of the content of the Profile Sub folder from the old PC into the Profile folder in Thunderbird on the caddy drive? This will then be my backup of the required data? Then, to get the data onto the new PC I connect the Caddy drive to that and transfer the Profile Folder from the Caddy Drive to the new PC - exactly where? Damn, now I've erased the default profile in the new PC and so it won't start up. I'll have to clear it with CCleaner Pro and reinstall it. Closing down now, it's 1.15 am

I understand where the confusion comes from. On the page with the video and instructions you followed, the opening paragraph says;

To move your data, copy your profile folder to the equivalent location on your destination computer...

while step 4. says;

From your Thunderbird profile folder, go up three levels...

which takes you to the Roaming folder with the Thunderbird folder highlighted/selected.

I find those directions to be unnecessarily complicated, because ALL you need to transfer to the new PC are the contents of the profile folder itself, which opens when you go to Help > Troubleshooting Information > Open Folder as described in steps 1, 2 and 3. Step 4 is not necessary at all. The solution I gave in the other thread to which I referred you to skips the Roaming\Thunderbird folder altogether and focuses only on the contents of the profile folder itself.

Now, before we proceed any further, kindly point out which terms I used that you don't understand so that I can explain better.

Since you already copied the entire Thunderbird folder from the old PC's Roaming folder to the Caddy, connect the caddy to the new PC, open the Thunderbird folder that it contains then open the Profiles folder inside it. You will see at least one weirdly named folder inside, with eight random characters making the first part of it, followed by a period and some readable name afterwards, for example xxxxxxxx.default. That weirdly named folder is the actual profile folder whose contents are what need to be copied to the new Thunderbird profile. The folder will also be large in size because it contains your years old emails. Please confirm that you are looking at that folder and not any other and that we are on the same page as far as the profile folder is concerned.

Hi again - I'm having to work both PCs at present as i get about 80+ emails a day and often need links in them to keep my other tasks moving. As the mail in the old profile grows I need to copy it afresh each time I get ready for transfer. Maybe a bigger problem is that having deleted that weirdly named profile folder by mistake i then couldn't pen Thunderbird. I uninstalled it and then reinstalled it but it didn't correct it. So now I'm about to download a new version and install that. I'll come back when i have some progress and a new Profile Folder filled with the up to date mail. Thanks, John

I followed the instructions for copying the default profile from the old PC (with Th-bird closed)

Then I got 2 half screens of File Explorer open on the new PC, with a brand new install of a newly downloaded Th-Bird in one and the Caddy contents in the other. I got the Roaming screen open in the PC and closed Th-Bird, then I copied the new default profile (5.91 GB) off the Caddy and pasted it into the default profile on the new PC. Now I'm about to start Th-Bird and keep all fingers crossed.

Now I am back at that head=scratching situation where I've apparently done everything but Th-bird is still empty? How do I get it to recognise that it's full of mail? Nowhere have I seen anything that addresses this so I'm taking it that it should have happened ???? Once again I'm baffled, probably by a simple click on something else?? I hope?? Can you explain it Sans? John

I got the Roaming screen open in the PC and closed Th-Bird, then I copied the new default profile (5.91 GB) off the Caddy and pasted it into the default profile on the new PC

If I understand correctly, you copied the profile folder from the caddy to the profile folder on the new PC, so the copied profile folder ended up as a subfolder inside the default profile on the new PC. Is that what you did? If so, then that won't work. Let's try and put things into perspective using hypothetical names for the weirdly named profile folders as follows:

1. On the old PC, the profile folder is named 12345687.default. When you go to Help > Troubleshooting Information > Open Folder, File Explorer opens showing the contents of this folder, among them are subfolders named Mail and ImapMail. These two subfolders are where Tbird stores your messages, so they constitute the bulk of the profile folder in terms of size. You can confirm this by checking their sizes.

2. In the caddy drive, you have a fresh copy of the old PC's profile folder named 12345678.default just before you transfer it to the new PC. This folder is an exact replica of the one in 1. above.

3. On the new PC, the new Thunderbird installation created a default profile whose folder is named abcdefgh.default. If you go to Help > Troubleshooting Information > Open Folder, File Explorer opens showing the contents of this folder, among them are subfolders named Mail and ImapMail just like on the old PC in 1. above.

4. So, what you did in the last attempt, was copy the 12345678.default folder from the caddy and pasted it into the abcdefgh.default folder on the new PC, correct? So, the abcdefgh.default folder contains the 12345678.default folder as one of the subfolders it contains, correct?

Correct Stans. So I closed Thunderbird, opened up the "12345678.default" folder, deleted everything in it except the extra "12345678.default" that i'd put there, and then moved that folder up a level so that it replaced the original "12345678.default". "BINGO" I thought, that'll do it. Opened up Thunderbird..... waited for the magic to happen..... Zilch! Now, that must be my fault as I'm the one trying to open it, but I must be missing something here somewhere. Maybe it's because last night I tried putting in the account details for 2 of the 3 mail addresses i use in Thunderbird. These do show up in the Inbox table on the left, but I could not find the password for my jreed198@btinternet.com email address so that one is missing. If I now delete the two addresses will the program now pick up all the mail I've copied over? ie - How do I get Thunderbird to start up using the default profile that I've copied over? This must now be the 10th or 11th attempt so I'm still doing something wrong, or missing this last step - is there another step or does switching the Thunderbird on start using the new data if everything is where it's meant to be? I'm baffled, but I accept that I must be missing something. I'm now going to copy the latest version of the profile and try again to transport it. But I'll also uninstall the Thunderbird and install a new blank set up ready for it. John

Before trying anything else I sent a test message from jreed198@btinternet.com (my main address) on the old pc to grizzlygrandpa and askjohnreed, the 2 addresses I added to Thunderbird on the new PC last night. They appeared in my Firetrust Mailwasher program first, as usual with my mail, and then when I went to Thunderbird they download there too - so the mail will get through (and to my main email once i find the password) BUT that doesn't achieve the main object which is to avoid losing all the mail from the past 3 years. If I now succeed in copying/moving the up to date default profile folder correctly is Thurderbird meant to spring to life on being opened showing a duplicate of the one on the old PC? Is there anything else to click? John PS: I do appreciate your help, I'm just frustrated at this key step taking so long in the middle of my starting 2 new projects. Thanks, I see a lot more now than I did, even if i still sound like an old duffer!

No need to uninstall and reinstall Thunderbird because that doesn't affect the profile folder. It only affects the application files, which are stored in C:\Program Files\Thunderbird and/or C:\Program Files (x86)\Thunderbird. Since you've uninstalled/reinstalled Thunderbird multiple times, I strongly suggest you perform one final clean reinstallation as follows:

Open Control Panel and uninstall ALL versions of Thunderbird if more than one is listed. I remember you mentioned IObit Uninstaller Pro. I generally don't recommend using such utilities blindly, but in this case, you can go ahead and use it for a clean uninstall of Tbird since you have a backup copy of your Tbird profile in the caddy. Double-check that IObit uninstaller cleans up the Thunderbird installation directories in the Program Files folders.

Wilco - have to get dressed and have lunch first though. I've been beavering away at PC work since i got up, my wife brought me a cup of tea and some biscuits to keep me going! - Thank You John

After the IObit uninstaller removal of Thunderbird, install a fresh clean copy of Thunderbird and launch it. It will load the default profile which doesn't yet include your old emails from the old PC. Open this default profile folder, hypothetically named abcdefgh.default, then Quit Thunderbird.

With Thunderbird not running, select EVERYTHING in the open abcdefgh.default profile folder and delete them, rendering it empty. Keep this empty folder open.

Now, open the freshly copied 12345678.default folder in the caddy so that you're viewing its contents in File Explorer. Put the two File Explorer windows side by side if you must. Select EVERYTHING the 12345678.default folder contains, then copy and paste them into the empty abcdefgh.default folder. This is where you're messing. You've been copying the 12345678.default folder itself, instead of its contents.

This is getting so frustrating I'm almost ready to kick Mozilla into touch completely and head off to Google mail and Chrome. I seem incapable of dropping the file in the correct place I've uninstalled and installed Th-bird twice more now, but that doesn't remove the three email accounts I've added (and have no idea how to remove). So I went back to the old PC where another 100 emails were downloaded from British Telecom and then repeated the copying - BUT I tried to simplify it by only copying the contents of the last level of folders with a the Profile title in there. It didn't work. I've been copying, pasting, moving files over various levels for about 33 years now since starting off on an Amstrad 128 and then getting a PC built for me by someone in the RAF - I was an Army Major back then (wasn't Windows 3.1 so much better than what went before?!!) - so I'm really angry with myself for not being able to finish this. I'm going back to your instructions again, I have to copy and paste like to like and I should surely get a "Tick to Replace" message if I'm replacing similar files.

Concentrating harder to do this as you last directed: With Thunderbird not running, select EVERYTHING in the open abcdefgh.default profile folder and delete them, rendering it empty. Keep this empty folder open.

Now, open the freshly copied 12345678.default folder in the caddy so that you're viewing its contents in File Explorer. Put the two File Explorer windows side by side if you must. Select EVERYTHING the 12345678.default folder contains, then copy and paste them into the empty abcdefgh.default folder. This is where you're messing. You've been copying the 12345678.default folder itself, instead of its contents.

Don't worry about the three email accounts you added. These will be gone once you empty the abcdefgh.default folder. There won't be anything to replace because the target/destination folder, abcdefgh.default, will be empty after you delete everything from it.

Right, - After more hours of no success and not even being able to open Thunderbird on the new PC I went to the User Data (after my 3rd re-install of new versions of Thunderbird) and very carefully opened up the Caddy version of the 123etcdefault and then I emptied that file on the new PC and am now copying those contents in from the Caddy to replace what was there - uho - it's finished,,,,, Fingers crossed!!!

Damn - still Thunderbird won't open! I'm flumoxed, stumped, pissed off and just up against a brick wall.

It has to be simpler than I'm making it, but I can't see where I've gone wrong this time - I'll do some more checks at all the levels through the program and see if anything stands out.

Thanks, John

1bk22mqi.default - is now 5.92 Gb and sitting in the right profile in its own correct place - but my Thunderbird program can't access it. I don't see why?

I'll have to try again on Fri I think, we'll be out a few times tomorrow seeing individual family members. Thanks.

Hi Stans - I had to give up on this for sometime to keep the rest of my life moving, but following our 53rd Wedding Anniversary yesterday I sat down again this evening for a determined attempt to succeed. This time I figured that if i went half way between the initial instructions and your much more detailed version I would be able to visualise the process and overcome not being able to get Thunderbird to run (so i couldn't get to the Help and troubleshooting buttons). I copied the Thunderbird Folder from Roaming on the Old PC (after closing Thunderbird there), connected the Back up Drive to the new PC and used the Users/jreed/AppData/Roaming path in the new PC Drive to find the "Thunderbird" Folder and delete it. Then I replaced it with the copy of the Thunderbird Folder from the old PC. Then I tried to start Thunderbird, it took longer than I expected, but that made me hopeful as I haven't been able to run it successfully for about 2 weeks. It flashed an address book error of some sort but then opened up and my old mail for the 3 addresses with all the old mail slowly appeared - What a Relief! Thanks for the help, your talking me through it helped me to see what was needed. John

Information on the restore is spot on, but I ran into an issue with Win 7 Pro security.

After restoring the profile information to the new laptop (and new userid), Thunderbird kept telling me that it could not find a valid profile. I finally opened a command prompt to type the prefs.js file and was promptly told that 'Access Denied'. I know that I should be able to resolve via the windows security, but have been lazy. I've just started the app in administrator mode on the new box and have not had a problem.