when you build the executable, in the installation tab there is an "Advanced" button, click to get into that screen, in it it shows the checkbox for runtime engine. when it is checked, by default all the components will be included, which you probably don't need. uncheck the ones you don't need and save the script, and build installer. it should be smaller.
also, once the installation files are generated, these files are normally created:
data.cab
install.msi
setup.ini
instmsi.exe
instmsiw.exe
setup.exe
Only the first two files are really needed by the OS. If the build does not need runtime engine then the package should be even smaller.
-Joe