I have duel email for the same address

You'll need to explain in more detail what that means.

I have two lists on the left like this xyz@comcast.net inbox drafts sent archives 2016 trash xyz6@comcast.net inbox sent archives 2016 trash local folders trash outbox

Are these two separate accounts, i.e. each with it's own password?

I think Thunderbird might be installed twice

That's unlikely. Even though you can install Thunderbird multiple times, you'd need to choose a different installation directory each time.

and don't want to unstall as I will lose my address files again.

Re-installing the application does not impact the profile, unless you deliberately chose to delete the profile in the process. http://kb.mozillazine.org/Profile_folder_-_Thunderbird

no both email address are the same

What is the account type for both accounts - POP or IMAP?

both of the emails com in thru a POP account with comcast

Occasionally users find that they have two copies of the same account and whatever they do in one is mimicked in the other. Alarmingly, that means if they delete one, both vanish. So I can't advise you to do the obvious thing and delete the second instance.

If it were an IMAP-connected account I would just delete both instances and reinstate it, knowing that it would be refilled from the server. But as yours uses POP, we have to tread more carefully as what you have is your only copy of these messages.

So...

First, backup your data. You can just copy your entire profile, or use a utility such as Mozbackup. That's your insurance against any further accidents.

Then I'd copy these messages to another location, such as Local Folders, or I'd export them.

Then I'd remove both of the offending accounts, close and re-open Thunderbird, and add it in again. It may just pick up the existing stored messages and you're good to go. If not, you can then re-import the exported messages, or move them back from Local Folders.

This addon can be useful for exporting and importing message stores.

https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

You are right partly. I did figure out last night what had happened. I did two things wrong after getting the computer back after getting the virous fixed by wiping the HD. Because I wanted MSN video play I had to upgrade to Wondows 10 to get it. I then activated the msn mail feature using my Comcast email. I think this is why I was getting two copies of the same email. each time. after deleting the email account in MSN I now only get one copy. but sitll have the listing for two on the left with the options. I can live with that. sh---. I just got a second message from you Zenos. so it is not fixed. I spoke too soon. I also found I have the same duplication of lists on my account settings. When I click on one it wont let me change them and says (an account with this name already exists, please enter a different address)

I think Zenos is right. I have two versions of thunderbird installed. but can only see one. I bought a lap top when the computer crashed and use a wifi connection with win 10 and it functions the correct way. given the difficulty of moving the address files from one to the other and backing up the files I think I will life with what I have. it would be nice if I could figure out how to sink them so they up date each other. I have to work on this. the lap to would be a great back up for files etc. Having to rebuild my address file again is not some thing I want to do. Also there is an email access on the comcast's web page but only updates address files if I am logged on to it.