Xfinity anti virus not updating

Run OS 10.6 on Mac Pro.  Have xifinity I net.  Downloaded free Mac antivirus (for 10.6) from Comcast while signed in. Never asked for account name or anything else.  File that came down was Norton_Internet_Security_4_Mac_EN.dmg.  I did this yesterday but this file was marked with a "date modified" of March 29, 2010.

 

I am being asked to subscribe or enter a key.  I can run the programs but no updating.  Comcast phone and chat no help. Transferred from chat key and phone line to nowhere.