Why Windows Installer prompting for a reboot

Windows Installer may prompt for a reboot if it installs over a file that is in use or the package explicitly requests that the installer reboot. It is easy to determine if Windows Installer prompts for a reboot because it installed over a file that is in use. The first step is to generate a verbose log file. In the verbose log file, look for the presence of the ReplacedInUseFiles property in the property dump. If this property is present with a value of 1, then the Installer will require a reboot because it overwrote an in-use file.