Hi Jeff.
Actually, since posting the question I have been able to solve the problem. To answer your question, CVI7.0 was not shown in the Add/Remove Programs section. Also, I did text searches on file name and file contents looking for strings like "National Instruments","NI" "Labwindows", "CVI", etc, and manually deleted all of those, including some normally hidden system files (a bit scary, but when you are desperate....). I also used Regedit to get rid of any references in Registry (also a bit scary). Still I could not load the new software.
The solution came when I used the Windows Installer Cleanup routine available from Microsoft. This showed up some installer/configuration files not located by text searches. Deleting these solved the problem.
John N.