Did you remove the old version first ?
If not,removal all traces of Norton using the removal tool click here
This includes your new version too.
You may need to check for redundant registry entries also,so run ccleaner click here
Then check with a manual search and remove anything related to Norton or Symantec.
Then reload your retail pack.
If no joy post back.
Yahoo was probably a bundled piece of software and can be removed from add and remove programs.