1. Install the Visual Studio 2008 QFE. Note this functionality is not available on the Express versions of the Visual Studio 2008 products.
2. Start Visual Studio 2008 and bring up Tools > Options > Debugging > General. If you are running under the Visual Basic Profile, you will need to check the box on the lower left of the Options Dialog marked “Show All Settings” before continuing (other profiles won’t have this option).
Set the following two settings:
Turn OFF the “Enable Just My Code” setting
Turn ON the “Enable Source Server Support” setting
3. Next, bring up the “Symbols” Page and set the symbols download URL and a cache location. Specifically, set the three settings below:
Set the symbol file location to be: http://referencesource.microsoft.com/symbols
Set a cache location. Make sure this is a location that your account has read/write access to. A good option for this is to place this path somewhere under your user hive (e.g. c:userssburkesymbols)
Alternatively, use NetMassDownloader for the .Net Framework which allows you do download .Net Framework source code in batch mode.
Full reference source code for .NET framework: http://referencesource.microsoft.com/netframework.aspx