Norton Internet Security Activation Problem

Hi, I initially installed Norton Internet Security 2007 (2 PC Pack) on both my Laptop and my wife's Laptop back in 2007/8. My own Laptop recently died and so we are now only using the one (my wife's). I have today downloaded a free update to Norton 2012 as offered on an email. Now I am being told that I cannot activate the new downloaded product due to me having installed Norton twice previously. Please advise what I am supposed to do next. I am not willing to purchase a new key, as I now only have Norton installed on one Laptop - and this was supposed to be a free upgrade. Can anybody help? Thank You