New version! - The Windows 8 Codecs (32 and 64bit) are stripped down versions of the Win7codecs and the majority of these instructions apply to those releases also. Haali, FFDshow and the Gabest filters are removed from the Windows 8 Codec releases. The Windows 8 Codecs are also compatible with all versions of Windows 7.
If you need a feature such as Haali to be able to handle multiple audio files within an AVI or MKV file, you can install the Win7codecs onto any Windows 8 system instead to give you more decoder chain options to choose from.