What are some alternatives?
When comparing NSIS and InstallBuilder, you can also consider the following products
Inno Setup - Inno Setup is a free installer for Windows programs.
InstallShield - If your software targets Windows, InstallShield is your solution.
IzPack - IzPack is a one-stop solution for packaging, distributing and deploying applications.
WiX - Create a free website with Wix.com. Customize with Wix' website builder, no coding skills needed. Choose a design, begin customizing and be online today
Advanced Installer - Advanced Installer is a Windows installer authoring tool for installing, updating, and configuring your products safely, securely, and reliably.
CreateInstall - Professional installer software is an essential component for any software developer.