Are you new to Thunderbird, or is this new behavior?

The first step I recommend is a Check Disk to check the hard drive for any file errors.

I have in mind a "proper" Check Disk which will require a reboot. For Windows 10: Click on the Cortana search button on your task bar, just right of the Start button (see first snip below), type cmd in the search box, but don't press Enter. Above that, right click on Command Prompt and choose Run as administrator. User Account Control will ask if you are sure you want to run it. Click Yes.

Then you will see a window similar to my second snip. In that you type: chkdsk c: /f It will then ask you the same question as you see in my snip. Type "y", then the Enter key.

Then close that command prompt window, and tell Windows to restart. It will do the disk check before Windows fully starts. Let it.

If the problem still exists, then: Create a new profile in Thunderbird for testing

If the problem still exists, then backup your e-mail, uninstall Thunderbird, reboot, then Download & install Thunderbird.

I typed in chkdsk c: /f and process ended there ...no questionasked...nothing.

Did you type it into the "Command Prompt" window? The one with the black background? If you typed "chkdsk" in there, no matter what was after "chkdsk", some text would come up in reply.

Also, you did not answer my question: Are you new to Thunderbird, or have you been using it successfully and this is new behavior?

I am not new to Thunderbird. This is new behavior...just over a week. My screensaver picture disappeared about the same time....now just black screen but still icons there.......After I type chkdsk c: /f nothing comes up until I hit ENTER.Then, it says "The type of the file system is NTFS. Cannot lock current drive....chkdsk cannot run because the volume is in use by another process.Would you like to schedule this volume to be checked the next time the system restarts? (y/n) "......

So,I type in y and hit ENTER. It says "This volume will be checked the next time the system restarts."

But, no place I can see for me to indicate Restart.

Go to the Start Menu and tell the computer to Restart.

When the computer reboots, it will run a Check Disk, let it.

It sounds like there are more problems with your computer than just with Thunderbird. If the problems still exist after running the Check Disk, then given your lack of computer skills, I recommend taking the computer to a technician to get the problems fixed.

I ran the Check Disk ...restarted....working again for a few emails.....quit and then started working again....so far is holding...thankyou Bruce Johnson for your help.