Team Foundation Server - label deletion when deleting builds

In TFS 2008 SP1 a feature has been introduced to allow you to retain Labels even when the associated build is deleted (either manually or via Retention Policies).

There are a couple of blog posts here:

• http://msmvps.com/blogs/vstsblog/archive/2009/01/09/turn-off-label-deletion-when-deleting-builds.aspx
  
• http://blogs.msdn.com/buckh/archive/2008/10/20/tfs-2008-sp1-new-setting-to-delete-a-build-without-deleting-the-build-label.aspx
  

Neither post is very explicit in that the particular web.config in which you need to add the setting, can be found here (assuming default installation):

%systemdrive%\Program Files\Microsoft Visual Studio 2008 Team Foundation Server\Web Services\web.config