how to 23 different project files correlate to each other in same C#.net 2008 solution file

Question

I am new to windows C#.net 2008 application that I need to maintain. When I look at the solution (.sln file), I can see there are 23 project files and I need to understand how all these projects are related to each other.
  Is this a way to understand how these projects relate to each other in the visual studio.net 2008 ide? (I know in the 2010 visual studio.net ultimate editon, there is a tool that setup a diagram to show you how the different projects relate to each other.) Would each project file have its own main module in it? If so, how would one project file call another project file if they both have a 'main' function?