Have you tried safe mode in your operating system? I have a feeling the issue is outside Thunderbird and may well reside in an antivirus product. Using windows safe mode will eliminate that (except for defender)

However I think you also need to reinstall the software as my XUL.DLL is 127mb not something around 121 GB. As a dynamic link library, the size should not change once installed and even between operating system versions will be generally the same range, although 64bit DLLs are traditionally larger than their 32bit equivalents, you report yours as 1000 times larger than mine.

Perhaps before you attempt a reinstall you might want to check the integrity of the actual drive under windows. This discussion on Microsoft answers offers instructions on how to do that using windows 10 and 11. Blue screens usually relate to real mode conflicts in Windows, that is kernel mode software, hardware drivers and other privileged programs. Thunderbird does not operate in real mode directly, referring such requests to the operating system to undertake on it's behalf. Other than hardware drivers, one of the few programs that routinely operate in kernel mode are antivirus programs. Hence they get an automatic suspicion when a blue screen occurs.

Thank you.

I have done a disk check and there is nothing wrong there.

As per my OP..... even in Safe Mode it crashed and got a blue screen.

I ONLY get the blue screen when using Thunderbird.

If I click on any nstmp folder........ it will "build a summary file" first. Sometimes it is even crashing during this process (which can take a couple of minutes). Even if it manages to build a summary file successfully, when I right click on the nstmp folder and try to delete it, it will crash every single time.

If I reinstall Thunderbird, I know it will keep my current inbox emails (as they are still on the email servers)..... but will it keep my sent folder, my trash folder, all the nstmp folders etc etc etc???

As per my OP..... even in Safe Mode it crashed and got a blue screen.

I had assumed Thunderbird safe mode on the help menu which has recently been renamed troubleshooting mode. Have you tried it? In the operating system safe mode?

You think I am being obtuse, but something is fundamentally wrong here at a very low level. Thunderbird should not be able to cause a windows BSOD, nor should there be something interrupting the compaction process to the point you have multiple nstmp files to appear as folders. Deleting the current files is not going to fix whatever is broken that is causing them to appear.

However I think you will do better if you hold the shift key and press the delete key to delete instead of using the menu. The shift delete bypasses the normal copy in the trash folder (immediate delete) which will be consuming disk space you say you do not have.

The physical location on disk for a folder is included in the same properties box as the repair button is located. The files are names nstmp. If you go the route of deleting the files in file manger, just make sure Thunderbird is not running, even as a task in the task manager.

I just did a massive clean-up of files on my C Drive and now have over 100GB of available space and Thunderbird still won't work.

When I open TB it starts downloading emails. Usually only 2 or 3 download succesfully and then it comes up with.....

"Unable to write the email to the mailbox. Make sure the file system allows you write privileges, and you have enough disk space to copy the mailbox."

I then close TB and reopen it and it will continue to download emails (very slowly)...... and the cycle repeats.

Interested Observer said

As per my OP..... even in Safe Mode it crashed and got a blue screen.

I had assumed Thunderbird safe mode on the help menu which has recently been renamed troubleshooting mode. Have you tried it? In the operating system safe mode?

You think I am being obtuse, but something is fundamentally wrong here at a very low level. Thunderbird should not be able to cause a windows BSOD, nor should there be something interrupting the compaction process to the point you have multiple nstmp files to appear as folders. Deleting the current files is not going to fix whatever is broken that is causing them to appear.

However I think you will do better if you hold the shift key and press the delete key to delete instead of using the menu. The shift delete bypasses the normal copy in the trash folder (immediate delete) which will be consuming disk space you say you do not have.

The physical location on disk for a folder is included in the same properties box as the repair button is located. The files are names nstmp. If you go the route of deleting the files in file manger, just make sure Thunderbird is not running, even as a task in the task manager.

Sorry..... I thought you meant Windows Safe Mode.

FWIW..... clearing 100+ GB of disk space did seem to help somewhat. I was able to successfully delete 3 or 4 nstmp folders and then delete them from trash as well......... before it crashed again.

I'll try the shift - delete option and TB Safe mode next.

UPDATE:

TB Safe Mode allowed me to delete ALL nstmp folders successfully. :)

My disc is now showing an additional 200GB of free space. :)

Unfortunately, I still have the problem of TB not downloading messages.

It will tell me it is downloading 1 of 21 messages, but after a minute or two it will just pop up the same error message.....

"Unable to write the email to the mailbox. Make sure the file system allows you write privileges, and you have enough disk space to copy the mailbox."

P.S. I have turned of Avast Anti-Virus and it still doesnt download emails.

This is my work email and I have already spent 5-6 hours trying to get this fixed........ so you can understand how frustrating this is becoming.

Just try in Windows safe mode. That will actually disable the AVAST you have installed completely. Most of them don't disable when they say they do, or leave your system in a basically non functional state by breaking networking. I do not know if it is deliberate on the part of the antivirus community, but their products appear to universally not do what they say they will well. Unless it is scan and scan everything they think they should when they think it should be done. That is why I now use windows defender. I am done with the paid products that slow my system and reduce my productivity without appreciable improvements to security.

You might want to try this https://support.mozilla.org/en-US/kb/rebuilding-global-database at times the database gets somehow muddled and Thunderbird spends all it's time working out what to index. A rebuild can take a long time to complete. You can monitor it using the activity manager (it is on the menu bar tools menu (alt will display the menu bar if it is not visible) It may help here I do not know for sure.

An inability to write to the file system is generally an external problem to Thunderbird with the antivirus being the most common thing also playing the the file space at the same time, although folk trying to sync their Thunderbird profile to things like google drive can also see the files simply not available at the time they are needed. As can streaming backups and network storage devices.