Why did ZoneAlarm need to reboot twice when I installed it on my XP computer. Updated September 30, 2017 11:03 After ZoneAlarm is installed on XP it must reboot complete the installation. When your computer reboots, ZoneAlarm will determine if a newer anti-virus engine or Antispyware engine is available. If a newer engine is available, ZoneAlarm will download and install it. To complete the installation, ZoneAlarm will need to reboot again. We apologize if you have to reboot your computer twice, but it will ensure that ZoneAlarm is properly installed, and that your computer's security is fully up to date.