I have a new/rebuilt computer which came with Windows 10 that I have downloaded Open Office and Thunderbird onto There are no other Microsoft files on this computer. My old computer died. all i have left is the external back-up drive. I need a step by step -clear explanation as to how to retrieve my old email files - outlook.pst- from my backup drive. I was able to retrieve all my other files that were backed up on this drive but not my email files which I need to use on Thunderbird. I have a Dell Optiplex 745 computer with plenty of hard drive capacity. Once this is accomplished I intend to wipe the back up drive and start with a new backup which will capture the new/old emails for the new system. Dale