I have performed the upgrade from Internet Security 2014 to 2015 at 2 PC's and had no problems. I have the operating system Windows 7 Home Premium and have this carried out at a workstation and a laptop. The installation was done in about 6-8 minutes. I have in the old Code of only 4 days are valid is now deposited with the new activation code as a reserve activation code. This should automatically activate after 4 days. I've been using since 2012 and Kaspersky Internet Security had so far no problems.