Sorry
dwlpl, maybe it's me (been a long day), I know you have looked at the files, but I still can't fathom whether you have downloaded RegCleaner and looked at the initial software list. If you haven't then that's your next best bet.
Either way, if still no luck a similar program called RegSeeker -
HERE - has a useful 'search' facility. Once downloaded go to second item down in the left hand column and click 'find in registry'. Put 'Symantec' in the search box and tick all the 'Keys_____search options' below and see if it finds anything. Repeat likewise for Norton. (Could also try their separate 'search files' option, even though you've been there).
As a final suggestion, Symantec do a (free/downloadable) removal tool for many of their programs to get the final bits out not sorted by a standard uninstall. As far as Norton Internet Security is concerned, (as an example) there are different removal tools for different years, so you would need to know if your original program was 2002...2005, etc. Likewise I believe with their other programs. I'll leave you to do a search on the
Symantec site.
Good luck.
BST