Annotate feature was not available out of the box in VS2005.It came only when you install the Team Foundation Server Power Tools. After installing TFS Power Tools you have to type the following command to invoke the Annotate Viewer tfpt annotate <path_to_file> But in Visual Studio 2008 Team System with Team Explorer this functionality is built in,if you are working on any team project and want to use this functionality just right click any file and from the menu just choose "Annotate".
After clicking this option the file will be opened in the IDE with the change set numbers stated first followed by whom the change set was triggered and the date on which the change set was triggered.
If you click on any particular change set then this will open the full information about that change set in the above example i clicked on the change set 4424 so it opened the change set information window 4424 for me.
This approach can be very useful if you just want to look at the changes made to that file within the IDE, this comes very handy when you are working on that file and want to see who has modified it and for what reasons and what changes your team members have made.