I'm sharing this in the event the information may be helpful to someone 
else.

Today for the first time since I had the problems with loosing my 
windows installation, I opened thunderbird and tried to use its chat 
option.  The settings for a facebook chat account I use were gone.

Then I went through the procedure to create a new account.  I entered 
all the required information and clicked the enter button, but nothing 
happened.  Here's how I fixed it.

I backed up everything in my profile directory.  Then I deleted 
everything except the mail directory.  Next I started thunderbird. First 
it recreated a bunch of file in the empty directory.  Then it asked me 
if I wanted to set up a mail account.  I closed that wizard and tried to 
set up the chat account.  I was able to.

I went to this site
http://kb.mozillazine.org/Files_and_folders_in_the_profile_-_Thunderbird
where there's a list of the files in a thunderbird profile directory and 
what they do.
 From the backup directory I copied the files that contain the saved 
addresses (abook.mab and history.mab), passwords(key3.db 
<http://kb.mozillazine.org/Key3.db> and Signons.sqlite) and prefs.js 
which the site said contains all the mail server settings.

When I started thunderbird, my email accounts were there and so was the 
chat account.  It also let me add a new account.   I looked inside 
prefs.js and saw the settings for the chat account.  This tells me while 
prefs.js stores the account information, some other file is needed for 
existing chat accounts to be visible and new ones to be created.

Goodnight