XNA Game Studio 3.1 enables hobbyists, academics, and independent game developers to easily create video games for Windows, Xbox 360, and the Zune digital media player by using optimized cross-platform gaming libraries based on the .NET Framework in the C# programming language.
This release is incremental to XNA Game Studio 3.0 and contains many new features, including avatars, Xbox LIVE Party support, and video as well as enhancements to existing features. For the full list of improvements in this release, see the “What’s New in XNA Game Studio 3.1” section of the documentation once you have installed the product.

Instructions
1. If XNA Game Studio 3.0 is installed, uninstall it before proceeding..
2. Install Microsoft Visual C# 2008 Express Edition or Microsoft Visual Studio 2008 Standard Edition or higher.
3. Obtain the latest updates for Visual Studio from Microsoft Update.
4. Download and run the Microsoft XNA Game Studio 3.1 installer.
5. Follow the instructions displayed during setup.
6. Launch Visual Studio 2008 from the Microsoft XNA Game Studio 3.1 folder on the Start Menu.