Try closing TB and deleting the parent.lock file in the profile folder.

To open your TB profile:

- TB menu > Help > Troubleshooting Information

- click the Application Basics > Profile Folder 'Open Folder' button

If that doesn't work:

Close TB and open the Profile manager. Select the profile you want to use by default > check 'Use the selected profile...' > click 'Start Thunderbird'.

Also make sure TB menu > Settings > General > System Integration > 'Always check to see...' is enabled and click the 'Check Now' button.

Hi Ed, -Deleted the "parent.lock" file successfully but message remained on start, blocking my access to TB -Uninstalled TB and re-installed TB but message remained again blocking my access to TB -With message blocking TB opening page access I have no access to menu icon (=)/ help menu/ trouble-shooting -The problem and the message is now the same with Firefox ("Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window")

More Help please Ed Malcolm

Did you try what I mentioned using the Profile Manager?

- press Windows Key+R on the keyboard. A Run dialog will open. In the Run dialog box, type: thunderbird -P. You can use -P, -p or -ProfileManager (any of them should work)

- select the profile you want to use by default > check 'Use the selected profile...' > click 'Start Thunderbird'.