If you used IMAP on old computer then all emails were stored on server, so installing Thunderbird and creating a new existing mail account to same email address will connect with server and display emails. If you used a POP mail account, then after creating a new pop account, it would only download anything that is currently in the server Inbox. However............................ If you can remove the hardrive from the old computer and get access to it via new computer using it like an external hardrive, you may still locate your old profile folders. They would be stored in this location: * C:\Users\<Windows user name>\AppData\Roaming\'''Thunderbird'''\ The following info is an option you can use providing you have access to old hardrive, but if you have already created new mail account on new comp[uter then you cannot use this without overwriting. So, ask about Importing mbox files if this is the case, otherwise................. Install Thunderbird on new computer, run, but do not add an account. Exit Thunderbird. This will create a default profile. Access old computer hardrive. * C:\Users\<Windows user name>\AppData\Roaming\'''Thunderbird'''\ Copy the 'Thunderbird' folder. Access new computer here: * C:\Users\<Windows user name>\AppData\Roaming\'''Thunderbird'''\ This is the new default profile. Delete the new 'Thunderbird ' folder. Paste the copied 'Thunderbird' folder from old hardrive into the 'Roaming' folder. Start Thunderbird.