Trying to install the Norton Antivirus I got an error message
That is probably an issue with the version of Windows that you have installed. From your statements I can see you have a 64 bit version of Windows. The new application you installed runs on a 32 bit platform hence the message. Probably you could install a 32 bit version or obtain a correct Norton Antivirus that is supported by the version installed
This issue that you are having is a known issue with Norton. What you need to do is Run the Live update to fix it. In the menu bar click go then Applications then go to the Symantec Solutions Folder after that double click Live Update then click on Update everything now.
Once you have done that restart your computer then run the update again just to make sure you have updated it successfully.
Hope this helps!