Can't remove corporate Symantec Antivirus

While I was emplyed by a large defense contractor, I installed the corporate version of Symantec antivirus in my home computer. I have since retired, and the corporate version is no longer being updated. I have tried to install Norton AV 2012, but I get a mesage saying I have to remove the old version first. Then when I try to remove it from the Control Panel, I get a message saying that I don't have the necessary privileges. How do I get rid of the corporate version so I can install a newer one? I don't think I should have to pay Norton for help installing a product I purchased form them.