Note that the update requires:
- Microsoft Visual C# 2005 Express Edition SP1
- That you run C# 2005 Express Edition at least once prior to installing the XNA Game Studio Express.
- That you register C# 2005 Express Edition prior to installing the XNA Game Studio Express.
If you're upgrading from the 1.0 version of XNA Game Studio Express you do not need to uninstall that version first.
You can download the XNA Framework Redistributable here.