There's a quote about cold dead fingers.
Remember when we only had 2 choices for installers?
InstallShield -- A lumbering dinosaur lacking grace and agility. Typically added 8-10MB of data to any installer. Often requiring brain surgery to uninstall.
Microsoft Installer (MSI) -- a systemwide installer system that, if it fails, prevents installation of any program requiring it. Countless tech support hours have been spent trying to remove, update, or otherwise make MSI do something useful.
Fortunately there are many installer builders now, and most are very space efficient and just plain work. Nullsoft (makes of Winamp) wrote their own installer. I've used AGInstaller by Agentix and it was pretty cool. Both of them only add about 250kb to the download package. AGInstaller could be fully scripted to run a batch file or executable as well as verify certain conditions and read system variables.