XNA Game Studio Express 1.0 Released
XNA Game Studio Express 1.0 have been released! This version now allows you to run XNA Game Studio Express on Windows Vista.
You could download it here at http://www.microsoft.com/downloads/details.aspx?FamilyId=12ADCD12-7A7B-4413-A0AF-FF87242A78DE&displaylang=en
However, there might be serveral issues that you might be facing that's stopping you from installing it. Here's something that might be of some help. http://msdn2.microsoft.com/en-us/xna/aa937796
Some exciting new features such as Bitmap Based Fonts, 3D Audio, Windows Vista support, Game Packaging and more!!!