I can't downlaod Norton Antivirus 2012

For the past several years, I have automatically renewed my Norton Antivirus Subscription over the internet.  I have never had a problem downloading it before.  Tonight I tried to download Norton Antivirus 2012 to my computer, and I received a message saying I couldn't complete the download because I didn't have the right system requirements. I have Windows Vista.  The version I have been using is Norton Antivirus Classic 2011.  I didn't see where there is a 2012 Classic version.  What should I do?