The CrystalReport Viewer control is a .Net assembly. By default, when you create a new .net 4 Windows Form application, it uses the .net 4 Client Profile framework, not the standard .net 4 framework. After I converted my project (Properties-> Compile -> Advanced Compile Options - Target Framework) to the standard framework, the Crystal Report Viewer control became available under the Reports section.
I have yet to research what the differences are between the two types of frameworks, or why we need them...