Inno Setup

Inno Setup is a feature-packed installation builder. Features include a wizard interface, creation of a single EXE for easy online distribution, support for disk spanning, full uninstall capabilities, customizable setup types, integrated file compression, support for installing shared files and OCX's, and creation of Start Menu icons, INI entries, and registry entries.

Key features:

Support for all 32-bit Windows versions in use today -- Windows 95, 98, 2000, 2003, XP, Me, NT 4.0.
Supports creation of a single EXE to install your program for easy online distribution. Disk spanning is also supported.
Standard Windows 2000/XP-style wizard interface.
Customizable setup types, e.g. Full, Minimal, Custom.
Complete uninstall capabilities.
Installation of files:
Includes integrated support for deflate, bzip2, and 7-Zip LZMA file compression. The installer has the ability to compare file version info, replace in-use files, use shared file counting, register DLL/OCX's and type libraries, and install fonts.
Creation of shortcuts anywhere, including in the Start Menu and on the desktop.
Creation of registry and .INI entries.
Integrated Pascal scripting engine.
Support for multilingual installs.
Silent install and uninstall.
Full source code is available (Borland Delphi 2.0-5.0).