It’s strange that one program would delete another like that. I did change the directory ‘Blender Foundation’ to ‘Blender_Foundation’ as I store my Python scripts beneath this directory, and some python scripts don’t like spaces in the path. Maybe that’s what caused the problem.
I guess I should have uninstalled via the Blender2.27 entry under the start menu. I just checked and while the menu still exists, there are no sub-menus below it now.
I’ll let Norton SystemWorks clean up the registry. Hopefully, that’ll also remove the entry in the ‘Add/Remove Programs’ feature in the control panel.