A hard drive might fail, but sometimes you can still get access by using it as an external hardrive to extract data. If you cannot retrieve the old profile from the old hard drive as there is no access to hardrive, then you cannot use the old profile on new notebook. All passwords are created and updated in the webmail account accessed via a browser. If you cannot remember password, then you need to use the 'forgotten password' link and follow instructions to gain access. Usually, an email will be sent to another email address or text message sent to phone. When creating the account, usually this information is setup in case of this type of situation. Once a new password is setup and you can easily access the webmail account, then you can use that new password in Thunderbird.