Nini is the uncommonly powerful .NET configuration library. The goal of this project is to provide developers with a tool that makes it easy to write highly configurable applications in a short amount of time.

Features

• Multiple Configuration Types 
  INI, XML, Registry, and command line
• Strong Variable Types
  String, int, float, etc. Eliminates casts
• Set and Save
  Add, remove, edit, and save configs
• Lightweight and Fast
  Small footprint, built for speed
• Merging
  Merge several configs into one
• Open Source
  Free for all purposes (full source code)

WiX  (Windows Installer XML) is a toolset that creates Windows installation packages from XML. WiX is an open source project, originally developed by Microsoft. Here’s list of links that may help you build installation using WiX.

WiX tutorial

IntelliSense for WiX .wxs files

differentpla.net

Rob Mensching’s blog