Inno Setup is a free installer for Windows programs.

First introduced in 1997, Inno Setup today rivals and even surpasses many commercial installers in feature set and stability.
Inno Setup is best used in combination with its free editor ISTools. Both Packages can be downloaded and installed directly here. An other thid-party tool which is Inno Script Generator can also be downloaded (the previous packages must be installed before).

Key features:

* Support for all versions of Windows in use today: Vista, XP, 2008, 2003, 2000, Me, 98, 95, and NT 4.0. (No service packs are required.)
* Extensive support for installation of 64-bit applications on the 64-bit editions of Windows. Both the x64 and Itanium architectures are supported. (On the Itanium architecture, Service Pack 1 or later is required on Windows Server 2003 to install in 64-bit mode.)
* 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.
* Support for passworded and encrypted installs.
* Silent install and uninstall.
* Full source code is available (Borland Delphi 2.0-5.0).

The step by step tutorial for innosetup is here.Tutorial: making an installer for your plugin in a few easy steps