Free Installers and Setup Utilities

Nullsoft (SuperPiMP|Scriptable) Install System
Generates self contained, win32 executable installer and includes uninstall support (installer can automagically generate an uninstaller); ability to display a license agreement, text or RTF; multiple install configurations and many other features

Inno Setup
Inno Setup is a free installer for Windows programs. Supports creation of a single EXE to install your program for easy online distribution. Creation of shortcuts anywhere, including in the Start Menu and on the desktop. Complete uninstall capabilities. Disk spanning is also supported. Full source code is available (Borland Delphi 2.0-5.

QuickInstall 2.0
QuickInstall 2.0 contains features like adding keys to the registry and two languages support. Windows 95, NT, 98 only.