If you want to extend your current backup set to include one more drive, you can do the following:

1) Open NORTON 360 main window.

2) Select Backup and open "Manage Backup Sets"

3) On "Summary" tab select the "Backup set name:" you want to extend.

4) On "What" tab make sure your new drive is selected.

5) Save Settings.

I think I did all of this, except when I set up my first Backup, I didn't call it by a new name, I left the DefaultSet name and eventually I saved the settings before running the Backup (I think). I may have just run the backup without saving my settings, which are definitely not the almost-useless DefaultSet.

I'll dump the first  (and latest) backup and do a competely new set with a new name this time and hope it works.

Thanks.

If you are going to keep the old backup drive and the new drive, you can just set up a new backup set, specifying the new drive as the destination.

Yes, I'm getting the hang of this, slowly. I've added some folders and excluded others and have saved the settings. But the Backup doesn't actually work. I'm getting an error message: Internal error. Not too helpful. So, if I can get a Backup to complete, I'll stick with Norton. Otherwise, I'll have to look elsewhere cause Windows 7 doesn't do it for me either, although its user interface is more intuitive. I'll call this discussion closed. Thanks for your advice.