手动删除下面的已经安装的组件：
Microsoft Silverlight 4 Developer 运行时Microsoft Silverlight 4 SDKMicrosoft Silverlight 4 Tools for Visual Studio 2010F# Runtime for Silverlight 4
和Microsoft Silverlight
然后再去http://www.microsoft.com/downloads/zh-cn/details.aspx?FamilyID=b3deb194-ca86-4fb6-a716-b67c2604a139&displayLang=zh-cn
下载Microsoft Silverlight 4 Tools for Visual Studio 2010 重新安装即可
