TB stopped retrieving new messages and trying to "reconfigure" my account to fix the problem, now I lost my old messages.

Question

[4/15/14 edit #3] I posted the requested troubleshooting information and made a backup of Profiles using MozBackup, so my remaining problem is the presence of two Inboxes, both receiving messages, and my not being sure which one can safely be deleted nor how to safely delete it.
[4/14/14 edit #2] T'bird's Help taught me where my "Profiles" are stored but I found I had no backup of them. However, I now discover that I have TWO Inboxes - hadn't noticed that quirk before. Thankfully, one of them still contains all of my old messages! The Inbox that still has all of my old mail is listed as a subfolder under "Local Folders" and the Inbox that I thought was my only Inbox is listed as a subfolder under the top folder whose name is my email address. Both Inboxes are now retrieving my new mail. Does this mean I have somehow created two accounts? If so, how do I get rid of the account that uses the Inbox that does not have all my old mail in it? I don't want to get rid of the wrong account but I suspect the "right" one should be listed under my email address, not under "Local Folders". If anyone understands this mess that I've created, I'd really appreciate some advice so I don't make things worse. At least I've now learned what it is that I need to back up.
[4/14/14 edit #1] Following is a major update of the problem I described before (see below). I disabled the Mail Shield portion of my Free Avast antivirus software and discovered that TB was again able to retrieve my email. Then I re-enabled Avast to see if it blocked TB again. It did not. So, apparently simply turning Avast's Mail Shield off and then back on again seems to have fixed the problem. However, I'm now left with the consequences of my having tried to "reset" TB as I described below, namely the loss of a very large number of emails that were stored in my Inbox. So the remaining problem I'd like help with is how to recover those seemingly lost emails. If they remain on my hard drive, where did TB store them and what specific files should I look for? I do have a backup of some of my hard drive (but nothing under Program Files), but I need to know how to identify them, where to look, and how to get them back into my Inbox without deleting its current contents. I'd really like to also retain their original dates, if possible. I'm running 64-bit Windows 8.1. [end of 4/14/14 edit]
TB suddenly stopped downloading my mail today. After I click Get Mail, I can see at the bottom of the screen a very rapid succession of messages; first the "connected..." message, then "checking...", then "downloading 1 of 10...", then finally, "No messages to download" after downloading absolutely none of them. I also noticed that my list of mailboxes was missing the very first entry that showed my email address as the account name. Figuring something major must have been changed in my account configuration, I went through all the settings but saw no problems. Finally, I decided to try to re-establish my same account. That did place my email address again back at the top of the mailbox listings as my working account name but it also created a worse problem. There were now no messages in my inbox, I suppose because I must have created a new account using the same name as the old one, whereas before there were thousands of messages that I had saved for many years (since this is a business). Then when I clicked Get Mail, TB downloaded 383 messages that had not yet been deleted from the server, giving then all today's date (another loss since their original dates were important). But after it finished downloading all of them, clicking Get Mail still does not retrieve any messages past the time that it stopped retrieving them earlier today. Those newest messages remain on the server - but now there are 14 of them instead of 10. The same succession of TB messages appears at the bottom of the screen, but now it says "Downloading 1 of 14..." but still downloads none of them and ends with, "No messages to download". This sequence of messages will repeat as often as I try to retrieve mail but it can still count how many it is NOT downloading. Two questions: (1) Are the thousands of messages that were stored in my Inbox still stored somewhere on my computer and is there any way to recover them? (2) How can I get TB to start retrieving my current email again? I guess it's obvious that these are important problems to me and that I'm totally stumped. Many thanks in advance.

Answer 1

Sorry. Here is the Troubleshooting Info:
Application Basics
Name: Thunderbird
Version: 24.4.0
User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0
Profile Folder: C:\Users\Phil\AppData\Roaming\Thunderbird\Profiles\p8gz2q23.default
(Local drive)
Application Build ID: 20140316131045
Enabled Plugins: about:plugins
Build Configuration: about:buildconfig
Crash Reports: about:crashes
Memory Use: about:memory
Mail and News Accounts
account1:
INCOMING: account1, Local Folders, (none) Local Folders, plain, passwordCleartext
account2:
INCOMING: account2, [email protected], (pop3) pop.att.yahoo.com:995, SSL, passwordCleartext
OUTGOING: smtp.att.yahoo.com:465, SSL, passwordCleartext, true
OUTGOING: smtp.att.yahoo.com:465, SSL, passwordCleartext, false
account5:
INCOMING: account5, [email protected], (pop3) inbound.att.net:995, SSL, passwordCleartext
OUTGOING: outbound.att.net:465, SSL, passwordCleartext, true
Extensions
Check for Updates in Help Menu, 1.1, true, [email protected]
CompactHeader, 2.0.8, true, {58D4392A-842E-11DE-B51A-C7B855D89593}
Remove Duplicate Messages (Alternate), 0.3.9, true, {a300a000-5e21-4ee0-a115-9ec8f4eaa92b}
ViewAbout, 2.0.1, true, [email protected]
Extra Folder Columns, 1.1.5, false, extra-cols@jminta_gmail.com
Important Modified Preferences
Name: Value
accessibility.typeaheadfind.flashBar: 0
browser.cache.disk.capacity: 358400
browser.cache.disk.smart_size.first_run: false
browser.cache.disk.smart_size.use_old_max: false
browser.cache.disk.smart_size_cached_value: 358400
extensions.lastAppVersion: 24.4.0
mail.openMessageBehavior.version: 1
mail.winsearch.firstRunDone: true
mailnews.database.global.datastore.id: 9bbfa749-eb91-4c2e-9a9a-d0e0146e393
network.cookie.prefsMigrated: true
places.database.lastMaintenance: 1397067237
places.history.expiration.transient_current_max_pages: 52770
places.history.expiration.transient_optimal_database_size: 85415034
plugin.importedState: true
privacy.donottrackheader.enabled: true
Graphics
Adapter Description: Intel(R) G45/G43 Express Chipset (Microsoft Corporation - WDDM 1.1)
Vendor ID: 0x8086
Device ID: 0x2e22
Adapter RAM: Unknown
Adapter Drivers: igdumd64 igd10umd64 igdumd32 igd10umd32
Driver Version: 8.15.10.2702
Driver Date: 3-11-2013
Direct2D Enabled: false
DirectWrite Enabled: false (6.3.9600.16384)
ClearType Parameters: Gamma: 2200 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 100
WebGL Renderer: false
GPU Accelerated Windows: 0
AzureCanvasBackend: skia
AzureFallbackCanvasBackend: cairo
AzureContentBackend: none
JavaScript
Incremental GC: 1
Accessibility
Activated: 0
Prevent Accessibility: 0
Library Versions
Expected minimum version
Version in use
NSPR
4.10.2
4.10.2
NSS
3.15.4 Basic ECC
3.15.4 Basic ECC
NSS Util
3.15.4
3.15.4
NSS SSL
3.15.4 Basic ECC
3.15.4 Basic ECC
NSS S/MIME
3.15.4 Basic ECC
3.15.4 Basic ECC
ISP is AT&T, anti-virus is (free) Avast, Windows firewall