I'm not 100% clear what you're saying. You've reset your PC to factory settings and have re-installed Thunderbird, is that right? And now you are trying to set up your TalkTalk account? And when you type in the password to connect to the server, you get an error message saying 'password not recognised'?? If that's what is happening then it's not Thunderbird that won't accept the password, it's the TalkTalk server: that message indicates that the server won't accept the connection. When you reset your machine, did you uninstall Thunderbird first? Did you remove the passwords for the account?