NIS 2013 / 2012

Is it possible to use NIS 2012 with a 2013 subscription plan?  In other words, not upgrade the software.  I'm finding newly installed NIS 2013 to be very buggy on a number of my computer platforms: Windows XP and Windows 7.  I'd very much like to roll back to NIS 2012, but continue to receive virus definition and other updates throughout the year..