This is a drive letter mapping error. Copy the entire contents of both discs to a single folder on your hard drive. Run Setup.exe from that folder. It will not ask for disc 2 again.
initializes the InstallShield Wizard to unpack and transfer game assets to your hard drive. It typically requires: Administrative Privileges gta iv setup exe
Modern launchers handle the installation automatically. You won't typically interact with a standalone setup.exe unless you are navigating to the installation directory to troubleshoot. This is a drive letter mapping error