What version of Thunderbird are you using?

Thank you for taking an interest. This problem is on my wife's laptop which has been put away now. I will come back with the answer tomorrow.

The laptop is running on Windows Vista Home Basic. The version of Thunderbird was 12.0.1 which has just updated to 31.2.0 but this has made no difference to the problem

If you close each open window by clicking on the top right 'X' button, does it close one window at a time?

Yes,one at a time and it is always 40 windows that open

Try this:

Make hidden files and folders visible:

• http://kb.mozillazine.org/Show_hidden_files_and_folders

In Thunderbird:

• Help > Troubleshooting Information
• click on 'Show Folder' button

a window will open showing Profile Folder name.

• Close Thunderbird now - make sure all opened windows are closed. This is important.

• scroll down the list and locate this file : session.json
• delete the 'session.json' file
• Close window - top right X
• Restart Thunderbird.

Please report back on result.

More recent versions of Thunderbird changed a few things regarding the toolbars. So, if you cannot see your toolbars, but you can see a 3bar menu icon, I would recommend that you can enable all your toolbars to make life so much easier. See image below.

Success. Thank you very much

Good to hear all is ok. In the forum, could you select the response from me, which fixed the problem as 'Chosen Solution'. Then it will log this as solved and it will help others who read it.