Source : Free On-Line Dictionary of Computing

installer
     
         A {utility} program to ease the
        installation of another, probably larger, {application}.  It
        is also possible for {hardware} to have an installer accompany
        it, to install any low level {device drivers} required.
     
        The installer commonly asks the user to enter desired
        configuration options for the main program or hardware, and
        sets up various initialisation files accordingly, as well as
        copying the main program to a {hard disc}.
     
        Some badly designed operating systems require applications to
        provide an {uninstaller} because of the number of different
        files modified or created during the installation process.
     
        (1998-02-09)