If all the data are in the accounts, my suggestion is to do a full uninstall. You can download from thunderbird.net and if you have install problems, please post so we can assist. We can then assist in helping sign up for the gmail accounts. IF you had messages in a POP account on Local Folders, I suggest the first thing to do is to copy the profile to another place to prevent any further loss. Let us know when you're ready to continue. (TIP: after installing, go to settings>general and set thunderbird to notify you of updates, but NOT to automatically install them. That keeps you in charge.)

Hi, I already deleted TB did a reboot, downloaded new copy. Same problem. Also tried to restore from prior date and that did not work. I foolishly believed MS11 when it said "backups will automatically be made of your files". Looked at History and NOTHING had ever been saved. I truly have no idea what to do. I know the files are copied to somewhere on the hard drive but no knowledge of how to rescue them. Thanks for the prior advice. Patrecia Glau

Hi, I don't know what happened but today when I tried to create new accounts - it worked. I did still loose all my extra folders. Just hope my addresses are still there. Will make several backup now on exterior disk. Thank you the advice greatly appreciated I was afraid I was going to be forced to us MS app! Pat Glau

I was glad to assist. A suggestion: make sure the backups are readable. I regularly see posts here by users who have backups that they can't read or restore.

Hello again, To be honest I have no idea how to make sure what I save is readable. I use a separate backup disc by Suhsai and I also put my folders on a thumb drive. Do not trust the CLOUD. Do I need to change my methods? Computers used to fun but now they are just getting to complicated. Pat Glau

I share your concerns. To guarantee accessibility, exporting each message to EML may be best, but mbox format is more convenient as that contains all messages in a folder. One way to be sure of your backups is to use a free mbox viewer, such as the one at https://sourceforge.net/projects/mbox-viewer/ - It just unzips, not install. Some of the messages are clumsy, but it lets you see all messages outside of Thunderbird dependency. There are several free viewers, and here is a slightly fancier one: https://www.freeviewer.org/mbox/ The mbox files with thunderbird usually have an accompanying file with msf suffix. You can ignore those, as they are just indexes.

On that, I always do backups with the intent of being able to easily move to another PC or do a full reinstall. To do that with Thunderbird, here are steps that do work:

BACKUP

1. ensure thunderbird is not running
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media

RESTORE

1. ensure thunderbird is installed and NOT running
2. enter %appdata% in search window on task bar and press Enter key
3. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
4. start thunderbird and all should be there

This backs up the data, and also all the settings for thunderbird and accounts for a much easier move between computers. For me, this has never failed. And I do it every couple of weeks to avoid total loss.