Microsoft Silverlight Tools Beta 2 for Visual Studio 2008为啥无法安装?

错误如下:
An Error Has Occurred:
Silverlight Tools cannot be installed because one or more of the following conditions is true:

1. Visual Studio 2008 RTM is not installed.
2. The Web Authoring feature of Visual Studio is not installed.
3. A previous version of the Silverlight Runtime is installed.
4. A previous version of the Silverlight SDK is installed.
5. The Visual Studio Update KB949325 is installed.
6. A previous version of Silverlight Tools is installed.

To continue, please install or uninstall the appropriate products and run this installer again.

1、2两项都安装了
3、4、6都卸载了
5没发现
不知为什么总是无法安装，哪位装过了，指教一下，谢谢。


一个小老外的做法，很有效
安装程序会把东西解压到一个文件夹里，在安装界面上可以看到，先别关安装程序，来到那个文件夹底下，找到需要安装的东西，依次安装就行了


直接运行VS_SilverlightTools_Beta2_Setup.exe居然成功了。