re :''Deleted the default profile on the new computer so that I could replace it with default profile from old computer.'' If you actually deleted the profile folder name, usually called xxxxxxxx.default, where the x's are letters and numbers and replaced with old profile folder name, then you would also have needed to update the 'profile.ini' file to point to the new profile folder name. Normally, you install Thunderbird and run the first time to create a new profile folder name, but do not create any mail account. then you access the new profile folder name. Close Thunderbird. then you copy paste the '''Contents''' of the old profile folder name into the new profile folder name overwriting the default contents. then restart Thunderbird. re :''Deleted Thunderbird to start again.'' Uninstalling the program and reinstalling will do nothing to resolve the situation if you did not delete the Appdata/thunderbird files as well. At this point I would suggest you access the 'profiles.ini' file and update the info to point to the profile folder name. Thunderbird must be closed when doing this.