You need to recover your old Thunderbird profile from the hard drive and transfer it to your new machine.

[Suggestion - If you create a new folder 'c:\Mozilla\' you can then make a new sub-folder 'Thunderbird' to place your recovered profile. You will tell TB where to find it. (I like all my Mozilla profiles stored in a single main folder- easier to find and back-up).]

When you install(ed) Thunderbird on your new machine, a new default profile was created, but all your old preferences, settings and mail are on your old profile.

If possible, do not use Thunderbird with your new profile. If you follow the procedures given in the article link, it will prevent having to combine the data from the old and new profiles. If you did use the new profile, do not worry, you can still combine data, but the procedure is a little more complicated.

https://support.mozilla.org/en-US/kb/profiles-tb

TB-38.2 Win10-PC

Thanks, still having a problem. I found and copied my old profile into the Appdata file but now TB thinks it is already running. I close and restart TB but no help. (ps- I went back and uninstalled and installed again, now it can't find the profile.)

From the profile article there are instructions for Win7 but I have Win8 and can't figure out where to run this command:
C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe" -p 

so I can choose from the two profiles, as in the article: https://support.mozilla.org/en-US/kb/using-multiple-profiles.

If you uninstall and reinstall Thunderbird, another new default profile is created. Until you use the Profile Manager to tell Thunderbird the name and location of your old profile, TB will continue to use the newer empty profile.

If you accepted the default install location for TB, then your TB files should be in "C:\Program Files (x86)\Mozilla Thunderbird" or another location that you selected.

Important - Close Thunderbird before continuing. The command you are having trouble with is NOT entered into Thunderbird. On your Windows PC if you right-click the Windows Start key, on the taskbar, a flyout should open that contains the 'Run' command. This opens a Command line box, where you will enter the code

"C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe" -p

(include the quotes in your copy) Copy and paste it into the run window, then press 'Run' The profile manager will open.

The article link mentions an alternate method that should also work in Win7

When you give your profile a name, be distinctive - 'profileFran' as a name is easier to select than 'default', 'default user', 'default user 1', etc.

https://support.mozilla.org/en-US/kb/using-multiple-profiles

After you get your profile running, use profile manager to delete the unused profiles.

TB-38.2 Win10-PC

Okay, I now have re installed after deleting the appdata for Thunderbird and now have TB working with the new profile. I still need my old mail and address book. In the profiles folder I have two profiles, the old and the new. How do I combine them?

Your last response came just 4 minutes after my previous message. We probably crossed messages.

If your old profile contained all your mail and settings before the problem developed, AND you have not added new accounts, preferences or received new mail from a POP account. OR there is nothing in the newer profile that you cannot manually enter into your older profile, you should NOT have to move any data from one profile to the other. Just follow the procedure given in that message, to use the Profile Manager to enable the old profile.

TB-38.3 Win10-PC

Thanks for all your help. I found the run command and copy and pasted the command. When it runs it finds only one profile named default. I tried deleting that, didn't work, tried renaming, creating new, changing the path. Last time I copied the address from the file explorer and it comes up saying the TB is already running. Is there a way to just get my addresses? I'm ready to give up on getting everything.

Never mind I just copied the abook.mab from the old profile to the new and got my addresses. Do you think that would work for the old mail? Thanks again

You say that you deleted the files in appdata. Is this after you copied the old profile to that file? If that is true, then the old profile is NOT in that folder any longer. Or possibly you did not navigate to the correct folder in Profile Manager.

Your old and new profiles are typically in a folder named "Profiles". They will have different random 8 character filenames (like 'gu4ean8z.default' or 'tm2fkp9n.default' each of these files contain your entire profile. As to which one is the old profile that has all your mail, check the external HD and determine the correct filename. (lets use 'gu4ean8z.default').

Make sure to copy the entire folder into the Profiles folder in the appdata section. All that should be visible are folders with the random names. Nothing else.

Now close Thunderbird.

When you start Profile Manager, CREATE a NEW profile name -'fran', when you are shown the folder tree to select a location, navigate to the appdata section and find the files with the random names. Select the one that contains your old profile ( 'gu4ean8z.default'). Select it and Press 'Finish'. The file will be renamed to 'gu4ean8z.fran'. When you view the profiles in the manager it will show only as 'fran'

It is possible to copy individual files from one profile to another, but there are supporting files that may need to be copied, and you may have to copy for each mail account. See this article:

http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Thunderbird

TB-38.2 Win10-PC

I made a Mozilla folder like you said before and copied my old folder to it. I also backed up the new folder there before I deleted it from the Profiles folder, under Appdata. I did not confuse the file names. I did everything just like you said a couple of times. Whenever I try to use the old profile, I get a message saying TB is already running. I assume there is something wrong with the folder. I am giving up on using the whole folder. The last time I installed and copied in the address book it worked so I'm going to un-install and re-install again, copy in the address book. I will read the last link you sent and see about transferring more in before I try that. Thanks again.

I'm going to call this solved. I have my address books and emails back, by copying the files into the new profile. I don't know why the complete profile folder import wouldn't work but I'm satisfied with what I got.