Perkin was right - an ancient version (0.2.3, I think?) was installed, but not showing up in remove programs or anywhere else. I deleted it and cleaned out its remnants, used Revo Uninstaller Pro to completely remove Sigil, rebooted, then reinstalled.
But now I'm still left with the problem where the current version doesn't have all its proper menus as shown in
http://technomom.com/sigilnotools.jpg :-( Any suggestions there?
Thank you!
Cyn