Guys ....... Check this out
Written by Shawn Burke of Microsoft...
It's finally here - the launch of the .NET Reference Source project. This post (hopefully!) contains everything you need to know. Over the past few weeks, we ran a pilot of this feature and collected lots of great data that helped us work through some issues and understand where people were likely to have problems.
Please carry on with he following link
http://blogs.msdn.com/sburke/archive/2008/01/16/configuring-visual-studio-to-debug-net-framework-source-code.aspx
More on Scott's Blog
http://weblogs.asp.net/scottgu/archive/2008/01/16/net-framework-library-source-code-now-available.aspx
And Scott Hanselman's ComputerZen.com
http://www.hanselman.com/blog/NETFrameworkLibrarySourceCodeAvailableForViewing.aspx
Regards