Microsoft has released IIS Media Services 4.1. IIS Media Services 4.1 is an integrated HTTP-based media delivery platform

Do you already have IIS Media Services 4.0 installed?
This download adds additional features and enhancements to your existing IIS Media Services 4.0 installation, including:

Performance enhancements for the On-Demand Smooth Streaming and Live Smooth Streaming modules.
Support for managing Live Smooth Streaming publishing points programatically by using IIS Smooth Streaming Management REST Services.

Is this a new installation of IIS Media Services?
This download installs the features for both IIS Media Services 4.0 and IIS Media Services 4.1 at the same time.
IIS Media Services is a set of media-related extensions for Internet Information Services (IIS) 7 and higher. IIS Media Services provides an integrated HTTP-based media delivery platform, and includes:
Smooth Streaming. Enables adaptive streaming of on-demand media files for Smooth Streaming-compatible clients, including Microsoft® Silverlight®.
Live Smooth Streaming. Enables adaptive streaming of live media broadcasts for Smooth Streaming-compatible clients and for Apple® mobile digital devices.
Bit Rate Throttling. Meters the speed at which media is delivered to a player.
Web Playlists. Enables secure sequencing and server-side control of media content.

You can also download additional IIS extensions related to IIS Media Services:
Advanced Logging, providing real-time client- and server-side logging.
Application Request Routing, providing HTTP proxying and caching.
Transform Manager, supporting media workflows, watch folders, and batch encoding/transmuxing of H.264-encoded content for Smooth Streaming and HTTP Live Streaming.

Download for 32-bit
Download for 64-bit