XNA Game Studio Express (Beta) Download

http://msdn.microsoft.com/directx/xna/gse/

System Requirements and Prerequisites
Only supported on Microsoft® Windows® XP SP2 (all editions) at this time. Windows Vista will be available only in a future beta release of XNA Game Studio Express.
Hardware requirements are identical to those for Visual Studio 2005 plus a graphics card that supports DirectX 9.0c and Shader Model 2.0.
This release requires Microsoft Visual C# 2005 Express Edition to be installed before proceeding. You can install Visual C# Express from the Visual C# Express Download Page. However, other members of the Visual Studio 2005 line of products, for example Visual Studio 2005 Professional, can co-exist with XNA Game Studio Express (Beta) on the same computer.