NSIS (Nullsoft Scriptable Install System) is a tool that allows programmers to create installers for Windows. It is released under an open source license and is completely free for any use. NSIS creates installers that are capable of installing, uninstalling, setting system settings, extracting files, etc. Because it's based on script files you can fully control every part of your installer. The scripting language supports variables, functions and string manipulation, just like a normal programming language - but designed for the creation of installers.
You can download the newest and original NSIS software with source code using below links.