I'm sorry to hear about the trouble you're facing. It sounds like the recent Thunderbird update might have caused some issues. To retrieve your lost Address Books and second email address, you can try a few steps. First, make sure Thunderbird is closed. Then, navigate to your Thunderbird profile folder. You can find this by going to "Help" > "Troubleshooting Information" in Thunderbird and clicking on "Show Folder" next to "Profile Directory." In the profile folder, look for "abook.mab" for your Address Books and "prefs.js" for your email settings. You might need to replace these files with your backups if you have them. As for the 'side by side configuration' error, try reinstalling Thunderbird or repairing the installation. If your PC was indeed corrupted, you might want to consider running a system check or getting professional help.