Please download this tool it is specialized in removing Norton.
it will search your entire computer and delete any added registry Vaules.
download form here
This tool will not run in savemode.
This tool it remove all version of Norton 2003 - 2006
in some cases you need manually to disable the services ... you can go to Start -> Run -> MSCONFIG -> Services -> (( there will be around five services has "Symantec" word along with the name for the service)). you will be in need to uncheck the box for each service and try to run the tool.