In order to install, upgrade, uninstall, and patch the sql server 2008 instance on the system we need to call the setup.exe from the installation media.
The setup.exe is an unmanaged code which checks the basic pre-requisites to launch the actual Setup process. The basic pre-requisites check performed by setup.exe is
1) It checks for the presence of the .Net Framework with SP1. If not present, it will initiate the installation of the .Net Framework with SP1.
Note: The setup during the installation of .Net Framework 3.5 might say “Downloading from Internet”. However it actually loads the setup from local copy and does not connect to Internet.
2) It checks for the presence of the Windows Installer 4.5 and if it is not present it will install it.
After installing these pre-requisites, it asks for reboot. And if there is any pending reboot operation from previous installation, it will ask for reboot and exit with error code 3010.
The Logs for the setup.exe (unmanaged code) is located in %temp%sqlsetup*.log.
After the initial bootstrapping performed by setup.exe it calls the setup100.exe which is managed code which performs the actual setup process