ASP.NET Web API 2

New Features in ASP.NET Web API 2 - Part I - Dan Wahlin:

Implementing an API in ASP.NET Web API - Online Training Course for Developers @ pluralsight by Shawn Wildermuth

ASP.NET Web API 2 : The Official Microsoft ASP.NET Site

HotTowel.Angular and ASP.NET Web API 2 Compat | John Papa

ASP.NET MVC 5 (that includes Web API 2) requires minimum .NET 4.5
So that excludes using it with Windows 2003 (and XP).