This sounds like something is not fully deleted before installing a fresh newly downloaded Thunderbird from the official site.

If you have CCleaner, then please make sure it does not have access to any Thunderbird folder or file.

Clear the browser cache and the Windows Temp directory. If using....Shutdown any anti-virus software you are running. Download a new copy of the full installer; choosing appropriate language and OS from : https://www.mozilla.org/en-US/thunderbird/all/

Delete the directory directly... If 32 bit: C:\Program Files\Mozilla Thunderbird If 64 bit: C:\Program Files (x86)\Mozilla Thunderbird

Run the Thunderbird installer. If used: Restart the anti-virus program.

Thanks TH,

I don't know what CCcleaner is, neither do I have anti-virus.

I downloaded 52.2.0 and it installed and worked fine by the same process.

(uninstall via windows control panel, check empty program files etc, install from fresh download)

I did not enable automatic updater, but would be good to get that going when this problem is resolved.

Thanks

robshep said

After a few weeks of not using thunderbird, when trying to start it I get this message in a dialog prompt. "Could not find Mozilla Runtime" Thunderbird does not start. I've tried.... Re-installed Thunderbird from new download. Uninstalled Thunderbird, then re-installed. Rebooted computer (Windows 7 Enterprise, 64bit) These steps do not solve the problem No anti-virus, or anti-malware running. no other host problems. I have version: 52.3.0 Thanks Rob

This is very frustrating. I have followed various 'solutions' to the 'runtime' error, and have had absolutely no success to removing the 'Mozilla runtime missing' every time I boot up my PC. The only 'plus' is that if I click on cancel, the box disappears and Thunderbird is fully useable! I've used TB for years, without any problem. This has only recently happened after the last 'update'. I'm running Windows 10 Pro 64 bit. Fully updated. I have tried the following: 1. Switched off Windows Defender 2. Deleted the Thunderbird folder in Program Files x86 (+Mozilla maintenance) 3. Downloaded the latest EN version of TB 4. Re-installed it both in 'custom' and 'standard' versions - separately on different attempts. 5. Repeated 1-4 above and installed TB on another separate internal SSD drive in my PC. 6. I have also used Regedit to go through the entire Windows registry deleting every entry of 'Thunderbird' , and subsequently re-installing a complete 'vanilla' version of the latest TB..... (v.52.4.0 (32 bit) I get exactly the same result each time: Mozilla runtime missing. Ideas, please?

I do have a second question, totally different, to which any assistance would be much appreciated? I have created several folders in the 'Local' folder shown when the TB program opens, into which I have 'saved/moved' various mails from my inbox which I have received over the years which I use for important responses or records of correspondence. This 'Local' folder does not appear to be retained in the basic TB database - for example, when the actual program is fully uninstalled and re-installed. If I save the 'xxxxxxxxx.default' file prior to uninstall, I can copy/paste this in to the new Profile folder after the re-install, and regain access to these important mails subsequently. My main server is Gmail, but these 'Local' folders/files are not available to view on the Gmail server. My question is: how do I 'move' the 'Local' folder in TB so that this folder is available to be seen on the Gmail server when I log in there? Thanks! Ian