ANYWAY... I got very accustomed to TMR's reminder sound, so I tucked a copy of the .wav in my alarm-sounds folder (which I saw fit to name "noise", for some reason that escapes me now); and Lightning has a facility to choose different default reminder .wav sounds.
What kind of, OK, not just "kind of" but rather seriously scares me, is that Thunderbird doesn't have a distinct backup facility. Being able to restore all my journals, accounts registers and so on from external-drive backup is grand and all, but if I'm relying on software-specific data to also manage my time, remember birthdays and bills etc., then I darn well better be able to backup and restore my task data.
For this, there's an open-source project called MozBackup. MozBackup is pretty sophisto, but it does a couple things strangely. First, it stores archives with ZIP-format compression (password-protected, if you choose), but instead of the .zip extension it names files with a .pcv extension.
Second, the automatic-backup documentation is a wee bit vague. The gist of it is, MozBackup can take a command-line parameter that tells it where to find a backup-job config file.
The smart way to use this facility is to write a batch program to call MozBackup with its config file parameter, and use Windows Task Scheduler to invoke the batch file. For security's sake (and for sane recovery in the event of disk failure), you'd keep the config file, which contains your cleartext password, in an encrypted part of your drive, which hopefully you're also likewise backing up regularly to secure storage.