It is generally advised that you try to keep the inbox empty, rather than making subfolders. You can create new folders in an account separate from the inbox. http://kb.mozillazine.org/Keep_it_working_-_Thunderbird

What sort of separate account are you referring to? Where would these separate folders you refer to go? I did see that I wasn't using the most current version of Thunderbird so I updated it. Checked my diskspace settings. Now set for 20MB. I have plenty of empty space on my HD.

This sounds like an IMAP account. Correct me if wrong and you are using POP.

From the Menu Bar select File-Subscribe

See if you are still subscribed to the missing folders. If you are , unsubscribe and then subscribe again.

This is for IMAP only.

I've got a POP server. Thanks anyway :D

Then this is real confusing. POP email only connects to the Inbox on the server and does not see other folders there.

I meant that for the account, make separate folders rather than subfolders in its inbox.

I had made them directly off of my Inbox. Are you saying that I should make them directly off of my Named-Acct at the top of the folder tree? I did make some that way now, but how do I get my old messages into them (that remain on my server)? I originally showed 85 messages in my Inbox. When I lost the 3 folders my Inbox quantity went up to 289 messages. None of the missing folder's messages moved into my Inbox. (I was not using the current version of Thunderbird, but rather one that started with 34.xx)

I was able to go back to my Pop server and create the folders I wanted off of the top of my folder tree (as compared to my Inbox). I was then able to move my messages to their appropriate folders.

Thanks for all of your help!

Do not forget to compact your folders.