This is a common problem with Norton. Usually, this is due to
remnants (Files & Registry components) that are causing the
conflicts. Symantec has a number of technical notes about the
specific messages and resolutions.
Basically, you may need one or two stand-alone tools from
Symantec RNav.Exe or RNis--.Exe. These two tools will do
a cleanup of Symantec components. However, in some cases
you may need the Microsoft Installer Cleanup utility or a Reg
patch to get around these issues. Unfortunately, there are a
number of these types of problems and no one procedure or
tool will resolve them all.
I've personally been involved in over 20 of these install quirks
with Norton 2004 products. A word of caution, be sure to have
a backup of your system as some of these tools and processes
make changes to the Registry.