If you are referring to installations of Comcast's Norton Security Suite, you can only deactivate a previous installation if you exceed the allowed number of NSS installs (which is 7, I think). If that happens a screen will appear during the install process which will allow you to deactivate one of the previous installs.
Unless you have retail Norton products you cannot until such time as you exceed 7 systems that have Comcast NSS installed. If youhave retail products, you can look in www.nortonaccount.com however you do not have a Norton Account with Comast NSS as Comcast controls your account.
A veteran - whether active duty, retired, national guard, or reserve - is someone who, at one point in his or her life, wrote a blank check made payable to The 'United States of America', for an amount of 'up to and including my life.'