in the start menu type %appdata% and press enter delete the Thunderbird folder.

However I really see no point in doing that. It is almost always easier to fix what is there than start again.

With regard to pop mail. Have you logged into the relevant web mails and confirmed that the mail is still actually on the server in the inbox before you consider blowing away local copies.

Like I said, I already deleted the %appdata and the %local settings/appdata folders. When I reinstall, all the original mail accounts are there, or parts of them.

I tried to "fix" the accounts present. I'm left with a pop account (verizon) that Tbird says is a "special" account, and will not let me delete.

Pop mail servers have been verified. Not concerned with whether the mail is still on the servers, it isn't since Outlook Express downloaded them, and I have it unchecked to leave a copy on the server. Local mail files are stored in a folder off the route of C: making them easier to find than where Microsoft wants to put them.

The "import" options in Thunderbird are provided to gather stored messages (etc) from other email clients installed on your computer. They don't import from email servers.

When you add an account to Thunderbird, it connects to the server and simply tries to show you the messages stored on that server. It's not helpful to think of this as "importing"; it's just an email client doing what email clients do.

In general, with POP, a client downloads messages and deletes them from the server, so normally we wouldn't expect there to be anything to download or "import".

If you want to keep old messages on the server, you need to be careful. By default, Thunderbird will start collecting messages from a POP server and deleting them from the server. You should probably set it up offline and set it to leave messages on the server before allowing it to connect.

The mention of "special account" means that at some point in the past, Local Folders has been renamed. I don't know why users do this.

Deleting the Thunderbird folder under AppData or Application Data should kill it all. Another possibility is that the Local Directory setting for one or more accounts has been changed to a location outside the profile. I always discourage this practice because it leads to messes like the one you're describing.

Go to account settings, open the affected account and in its "server settings" page, check what it says for the Local Directory. This will tell you where the messages are being stored, and so possibly some other folders to delete. (But if you have really deleted the Thunderbird profile folder, these settings should already have been deleted.)

(Mine is a Linux system, so the pathname will be formulated differently to those seen in Windows or OSX.)