This does not sound like a Thunderbird problem. It sounds like a keyboard problem. Are you saying that you can use that same keyboard in '''any program''' eg: Word etc and you press 'a' key and get an 'a' printed but when you use Thunderbird to compose an email suddenly the 'a' key prints and 'E' ? I would have expected that this keyboard issue would apply to any program , Notepad, Word, etc. Check you have the correct language selected for the keyboard. 'Control Panel' > 'Regional & Language Options' > 'Keyboards & Languages' tab