I use since 2 years Kaspersky on my PC (Windows7) without problems, have bought Kaspersky Internet Security 2015 Uprgrade to extend my protection in 2015. After installation, I was only on the Windows Explorer to the Internet, via Mozilla or Google went nothing more only misreporting. So Kaspersky uninstalled. One week later retry the installation. Then suddenly the message "invalid activation key". Activation code entered after the information, the period for the activation code is exceeded. Am now at my wits, maybe at the end someone has a useful tip. Kaspersky I buy at least not again.