Something about unsupported, don't have exact error.
Before you begin: If you are using Norton Anti Virus Corporate Edition 7.x, some of these instructions will not work.
For the correct procedures, read the document How to update virus definitions for Norton Anti Virus Corporate Edition.
I have found some installs of the retail package do not fully uninstall and leave some well hidden registry items. I ran the Norton Removal Tool (linked in the question) - is that different from NONAV249.exe?
This information might be useful as well: information serverfault.com/questions/20927 I think my problem is that I have 64-bit Vista, but I don't have the 64-bit NAV installer.nonav249is a different app as far as I know.
You can also copy an file from the \SAV folder on any Symantec Anti Virus server.